Fine. You accept that Voldemort did rise to power, yes? Let that be one plot that had however many "different things to happen" but worked. That is one plot with one payout that is collected without being dependent on other plots and covers step 1.

In step 2 his plot depends on his most idealistic enemies breaking from their ideals. That is 1 "different things to happen". He maybe tries a lot of different time, and eventually the Aberforth Event occurs, so the plot progresses.

Step 2a is the same plot and includes another "different thing." After he kills Narcissa, his formerly idealistic enemies must claim responsibility. He has conditioned them to do this in the way he has spread terror and treated them, so it does not come out of the blue, but it is the second "different thing" for that plot.

It works and he is rewarded with a conflict without escalation, where he can continue to amass power while his own side does not get out of control and his enemies become more reasonable and less idealistic, therefore easier to manipulate and less unpredictable. This second plot covers steps 2 and 2a. He could continue at this point as he had, building power for a faction, taking different steps or starting different plots.

The third plot has the goal of unity and only depends on two "different things." The first is that he have an opportunity to step out of the game, the second is that he has an opportunity to step back in. Again, there is the throwing shit at the wall approach, here. He can set up situation after situation that might lead to an opportunity to step out or in, and take the ones that he expects to work best.

When this plot is completed, he is rewarded with control of a new third side in a two sided war. He can do what he wants with this new faction, execute any number of plots from this point forward. This covers steps 3, 4, & 5.

The fourth plot is what he is preparing for, but isn't executing as far as I can tell, taking over the government. Whatever this depends on, you know he's up to something and this is no worse an answer than many other reasonable answers.

I'm fairly certain that Voldemort is not planning a party, though. That was a joke.

Well, yes, if it was planned from the beginning. It could have been improvised. To summarize Percent_Carbon in a way that brings out the potential that the plan he explained was improvised... Step 1. Conquer Britain as Voldemort. Doesn't work as well as hoped, Britain is divided, not united. Step 2. Use power to try to set up a situation that you think you can exploit later. Wait years before you see a good way to exploit it Step 3. See the way Harry Potter came out, see an opportunity to conquer a united Britain, and go for it

Probability is in the mind. If you're that much better at chess than you opponent, you can execute excessively complicated traps just to amuse yourself, and still be quite certain of victory. If Riddle knew more and thought better than Dumbledore, enough so that he can model his reactions precisely (as he seems able to) then what seems like an unlikely plot may be to Riddle merely an entertaining diversion.

That said, I agree that Godric's Hollow probably didn't go as Riddle planned.