The big platforms for Tug-of-War and Glass Bridge weren't real at all.
I should have realized then. I noticed my confusion ("If that drop was 20 meters and those walls are only ~3 feet high, I would be terrified and not casually walking by the edge like those guys"). But I failed to think of any hypotheses that fit the data.
Added: Ah, your explanation for why you fell for it makes perfect sense. I was so used to knowing it was real, that I didn't notice the one time it wasn't.
I recently watched Squid Game—both the original Netflix series and MrBeast's real life version. Then I watched every video I could find about how MrBeast's Squid Game was made. I was surprised to learn that MrBeast used a whole bunch of CGI (computer-generated imagery). I had taken its realty at face value.
There are four places I know of where MrBeast used CGI.
The sky, smoke and dust are all plausible. But the big giant platforms had to be CGI. Using such platforms in a real-life game would be ludicrously dangerous, especially without safety harnesses. Real platforms would be unnecessarily expensive too compared to replacing backgrounds, which is part of VFX artists' standard toolkit.
Why didn't I notice?
First of all, the VFX team SoKrispyMedia is very good at VFX. But that alone isn't sufficient.
My experience of watching MrBeast's Squid Game reminds me of a magic trick routine I used to perform. To the audience it looked like two separate magic tricks but they actually worked together. First I would perform a series of tricks that used a real regular deck of cards. Everything was pure sleight-of-hand. Once my audience had gotten used to the idea that I'm doing everything legitimately I would switch to a set of gimmicked (fake) cards. The effect was much stronger than when I started out with the gimmicked (fake) cards.
MrBeast (perhaps unintentionally) pulled off a similar trick. When I watch television and movies, I'm constantly scrutinizing each scene to figure out how the filmmakers created it. But most of MrBeast's videos are completely real. When I watched MrBeast's Squid Game it did not occur to me to question anything, even when the images onscreen were unrealistic. I wasn't on-guard for CGI trickery.
Unexamined Beliefs
Most of our beliefs never go through a thorough examination. There's just too much stuff going on. It's infeasible to question whether every rock and tree you look at is real. Perhaps you pick up a rock and question its legitimacy once or twice, but you can't do it for every rock you walk by every day. There isn't enough time in the day.
One way to define beliefs is to ask "what would you bet money on". But contemplating whether you would bet money on an unexamined belief modifies that belief the way forcing a quantum superposition into one of its eigenvectors destroys the initial state. The number of beliefs that go through a rational analysis is a tiny fraction of our total beliefs. The beliefs you would bet money on are an even smaller selection. Nearly all of our beliefs are (in their natural state) not things we would bet money on.
The problem of identifying what to question is a more fundamental challenge than reconsidering cached thoughts and thinking outside your comfort zone. Cached thoughts have been examined at least once (or, at the very least, processed into words), which is more examination than most of the beliefs flowing through a human brain. As for thinking outside your comfort zone, someone raised in a religious household who is merely 50% confident in Creationism is already most of the way to abandoning it.
Identifying the small bits of information that are even worth thinking about is the first step toward being less wrong.