So I'm open to changing my mind on this, but — having already been familiar with the evidence you posted below and having been adjacent to these circles for a long time — I'm very skeptical of both the claim generally that cults are endemic to the Rationalist community, and even moreso, specifically that it has anything to do with Rationalists holding beliefs loosely.

The Zizians are absolutely a cult. But did they get there by changing their beliefs too easily?

I think that's a really tough case to make -- one of their chief characteristics is their extreme slavishness to some particular radical views. These weren't people who jumped around often ideologically. Several of the Zizians (of whom there were never many) also weren't rationalists first. Where's the case that this is a result of Rationalism influence, or particularly that holding beliefs loosely was the problem? A handful of (the many) ex-rationalists forming a cult doesn't seem like strong evidence.

Leverage was certainly a high-demand social circle, and some people came out with some damage. I know others who were involved briefly, got no cult vibes, had no issues, and had a good experience with Leverage programs. Note also that a number of the "cult" claims came from Ziz and Ziz's friends, who even separately from Ziz influence have not tended to be particularly stable people — this doesn't mean they're wrong, but I do update a bit based on that. And Vassar definitely had a penchant for seeing vulnerable people near crisis and suggesting that they take drugs, which is generally stupid and harmful.

I don't think it's particularly useful to call leverage a "cult" even if there's some overlap, but if it is, is it because of Rationalists' willingness to change their minds? Again, I'm very skeptical. Vassar looked for people who were a little bit crazy/unstable, and did influence them to change their minds. But he didn't do this because he was looking to prey on them, and often engaged in ways that don't seem cultish at all — he did it because those were the people who understood him, because he was also a bit crazy/unstable!

Alternatively, what other explanatory factors are there for two cults closely adjacent to Rationalism?
1. Base rates. Have you been to the Bay Area? Cults are everywhere. Seriously, I suspect Rationalists are well-below the base rate here.
2. Very smart people who are also atypical as thinkers seem to be more susceptible to mental health issues, and in many cases these people from otherwise-vulnerable groups (e.g. almost all of the Zizians, many of the Leverage people). You definitely get some high-octane crazy, and groups of people that can follow certain types of reasoning can insulate themselves in a mental cul-de-sac, and then get stuck there because their blind spots block the exit and few others can follow the reasoning well enough to come in and get them.
3. Young people are easily influenced. As one Lesswrong commenter put it, "the rationalist community is acting as a de facto school and system of interconnected mentorship opportunities."

There's a lot of related discussion on these topics catalogued here, with Rationalists carefully dissecting these issues from various angles to see what the risks are and how they can make the community more resilient to them: https://www.lesswrong.com/posts/MnFqyPLqbiKL8nSR7/my-experie...