Turns out ISIS is now taking possession of Saddam's "nonexistent" chemical weapons stockpiles.

Your conservative revisionism does you no credit. I remember vividly the runup to the invasion because (I have remarked several times in the past) I was shocked at the demagoguery on display and the deep irrationality displayed by the American political system, and the case for invasion was not, in any way, 'Saddam has some corroded chemical weapons left over from our proxy war with Iran'. The case was, 'Saddam has active chemical warfare programs, active biological warfare programs, and most of all, an active nuclear bomb program, which justifies pre-emptive invasion before an American city was hit'. (Remember the aluminum tubes? The yellowcake? The Bush doctrine?) Your link even points this out, of course only to mock this without any explanation of why they seem to now think Bush pushed for an invasion because of some waste dumps. Look at your link! Look at what Cheney said:

And I think that would be the fear here, that even if he were tomorrow to give everything up, if he stays in power, we have to assume that as soon as the world is looking the other way and preoccupied with other issues, he will be back again rebuilding his BW and CW capabilities, and once again reconstituting his nuclear program. He has pursued nuclear weapons for over 20 years.

How does this match

Many chemical weapons incidents clustered around the ruins of the Muthanna State Establishment, the center of Iraqi chemical agent production in the 1980s. Since June, the compound has been held by the Islamic State, the world’s most radical and violent jihadist group. In a letter sent to the United Nations this summer, the Iraqi government said that about 2,500 corroded chemical rockets remained on the grounds, and that Iraqi officials had witnessed intruders looting equipment before militants shut down the surveillance cameras....Then, during the long occupation, American troops began encountering old chemical munitions in hidden caches and roadside bombs. Typically 155-millimeter artillery shells or 122-millimeter rockets, they were remnants of an arms program Iraq had rushed into production in the 1980s during the Iran-Iraq war. All had been manufactured before 1991, participants said. Filthy, rusty or corroded, a large fraction of them could not be readily identified as chemical weapons at all. Some were empty, though many of them still contained potent mustard agent or residual sarin. Most could not have been used as designed, and when they ruptured dispersed the chemical agents over a limited area, according to those who collected the majority of them. In case after case, participants said, analysis of these warheads and shells reaffirmed intelligence failures. First, the American government did not find what it had been looking for at the war’s outset, then it failed to prepare its troops and medical corps for the aged weapons it did find.

How does this justify not considering "Bush's claims about Iraq's WMD's ... thoroughly discredited"? (Why were there chemicals weapons there? Because, as the Duelfer report would have told you, that's where Iraq was shipping them for the UN to destroy but the UN decided some were too dangerous to destroy and sealed them away in bunkers, after which the site was razed; maybe not the best move, but understandable at the time. Take a look at the Duelfer report's description of the facility's post-Gulf-War-history and see if it remotely resembles Bush and Cheney's fears, and if it supports the contentions being made by the revisionists that 'really, Saddam had WMDs all along!')

Here Cheney is implying Hussein had 'BW and CW capabilities' and a 'nuclear program', which he might shut down, and then rebuild later. Look at the case GWB himself made in his state of the union address, his own words trying to convince America to invade Iraq because of the clear and present danger its active WMD program in the '90s and 2000s (not leftovers from the 1980s!) posed to America:

Almost 3 months ago, the United Nations Security Council gave Saddam Hussein his final chance to disarm. He has shown instead utter contempt for the United Nations and for the opinion of the world. The 108 U.N. inspectors were sent to conduct— were not sent to conduct a scavenger hunt for hidden materials across a country the size of California. The job of the inspectors is to verify that Iraq's regime is disarming. It is up to Iraq to show exactly where it is hiding its banned weapons, lay those weapons out for the world to see, and destroy them as directed. Nothing like this has happened.

The United Nations concluded in 1999 that Saddam Hussein had biological weapons sufficient to produce over 25,000 liters of anthrax, enough doses to kill several million people. He hasn't accounted for that material. He's given no evidence that he has destroyed it.

The United Nations concluded that Saddam Hussein had materials sufficient to produce more than 38,000 liters of botulinum toxin, enough to subject millions of people to death by respiratory failure. He hasn't accounted for that material. He's given no evidence that he has destroyed it.

Our intelligence officials estimate that Saddam Hussein had the materials to produce as much as 500 tons of sarin, mustard, and VX nerve agent. In such quantities, these chemical agents could also kill untold thousands. He's not accounted for these materials. He has given no evidence that he has destroyed them.

U.S. intelligence indicates that Saddam Hussein had upwards of 30,000 munitions capable of delivering chemical agents. Inspectors recently turned up 16 of them, despite Iraq's recent declaration denying their existence. Saddam Hussein has not accounted for the remaining 29,984 of these prohibited munitions. He's given no evidence that he has destroyed them.

From three Iraqi defectors we know that Iraq, in the late 1990s, had several mobile biological weapons labs. These are designed to produce germ warfare agents and can be moved from place to a place to evade inspectors. Saddam Hussein has not disclosed these facilities. He's given no evidence that he has destroyed them.

The International Atomic Energy Agency confirmed in the 1990s that Saddam Hussein had an advanced nuclear weapons development program, had a design for a nuclear weapon, and was working on five different methods of enriching uranium for a bomb. The British Government has learned that Saddam Hussein recently sought significant quantities of uranium from Africa. Our intelligence sources tell us that he has attempted to purchase high-strength aluminum tubes suitable for nuclear weapons production. Saddam Hussein has not credibly explained these activities. He clearly has much to hide.

The dictator of Iraq is not disarming. To the contrary, he is deceiving. From intelligence sources we know, for instance, that thousands of Iraqi security personnel are at work hiding documents and materials from the U.N. inspectors, sanitizing inspection sites, and monitoring the inspectors themselves. Iraqi officials accompany the inspectors in order to intimidate witnesses. Iraq is blocking U-2 surveillance flights requested by the United Nations. Iraqi intelligence officers are posing as the scientists inspectors are supposed to interview. Real scientists have been coached by Iraqi officials on what to say. Intelligence sources indicate that Saddam Hussein has ordered that scientists who cooperate with U.N. inspectors in disarming Iraq will be killed, along with their families.

Year after year, Saddam Hussein has gone to elaborate lengths, spent enormous sums, taken great risks to build and keep weapons of mass destruction. But why? The only possible explanation, the only possible use he could have for those weapons, is to dominate, intimidate, or attack.

...We'll be deliberate; yet, time is not on our side. I will not wait on events while dangers gather. I will not stand by as peril draws closer and closer. The United States of America will not permit the world's most dangerous regimes to threaten us with the world's most destructive weapons.

I watched this speech live; no one was the slightest bit confused by what Bush meant. There was no subtlety. We all understood that he was saying. If you had told them that 12 years later, the most that could be produced as evidence was what was in your link, we would have been appalled, disgusted, and certainly not have changed our minds to think 'aha, so Bush was right!'

Where's ISIS mobile bio-weapon labs? Where's the anthrax strikes? Have they nuked Tel Aviv yet with Hussein-era nukes? Where are their nuclear scientists running a enrichment plant to purify uranium for a bomb? For that matter, where was the "advanced nuclear weapons development program" when the USA invaded? Are "2,500 corroded chemical rockets" used as IEDs really what Bush meant by "the world's most destructive weapons"?

No, Bush was dead wrong, was proven wrong by the invasion, and links like that merely show a modern version of the Dolchstoss - an incredible desperation of partisan types to rescue, to some degree, one of the greatest strategic failures in American history.