No, it's because one of the core team members made threats against everyone who said they were thinking of forking it: https://lukeplant.me.uk/blog/posts/why-im-leaving-elm/#forka...
Long ago I went to a local Scala unconference. At the time there were at least two popular web frameworks, and one of the authors was in attendance. [1] Chatting during one of the breaks, I asked him some question about his framework, something about testability of apps. He quickly grew enraged and shouted at me. I slunk off, wondering what I had done wrong.
At the bar after the conference, a few different people apologized to me for his outburst. Not him, mind you, just other people. I was like, "Aha, I recognize this. He's a missing stair." [2] He was clearly an asshole to people on the regular, but the community just put up with it.
That was the last time I went to a Scala event. Life's too short to put up with bullies, or people who accommodate them.
[1] I no longer remember which framework or which author.
The question is how they do react once they've figured it out, and Scala's come along in leaps and bounds in that regard.
If anything, you should be more wary of groups that haven't yet dealt with that problem, because they've had no chance to develop the relevant antibodies yet.
I mean, I get it, if you have a bad experience with X, it's going to colour your perceptions going forwards, being human be like that - but similarly to throwing away a dice because you rolled a nat 1 with it at an inopportune moment, it's far from the most rational response available to you.
Did they really clean things up? Or is it just talk about how things have changed? The way to find out for sure is for me to spend time in the community. It could be better, or the abuse could just be better hidden. And honestly, given the revolution in recent years in codes of conduct and DEI, I suspect my odds are better with newer communities, as there are now plenty of "antibodies" out there.
But all this tickled my memory. Wasn't their an FP advocate who was also an abusive jackass and far-right kook just a few years back? Yes, yes there was. And gosh, what community was he prominent in? Scala. So if I had waited 5 years and given Scala another chance, I would still have landed in a community where there was significant support for abusive behavior.
Maybe he was booted in 2019 or so? Hard to tell from the web. From his tweets, it look like he has crept back in. Is that because he and Scala are worlds better? or is it just the usual missing stair routine that I observed more than a decade ago? I don't know, can't tell, and won't be finding out, because there are plenty of other technologies for me to pick up.
A lot of that stuff can easily just enable a different set of broken stairs though.
Crafting a code of conduct such that it makes it easy to deal with both reactionary -and- wokescold flavoured bullies is something of an art form, and I've seen a number of communities manage to completely fail at one of the two albeit usually in a very well-meaning way.
Antibodies are great up until they give you an auto-immune syndrome, basically.
(I definitely saw the far right kook get defenestrated, though the community may still be sufficiently quokka to've let him sneak back in through a different door, I'm mostly an observer here - and mostly only looking at all because as a veteran code of conduct advocate I tend to find the various failure modes worth examining)
So "I've just demonstrated how it was [...] a reasonable heuristic" is simply unsupported here. If it's working for you, great, maybe you're encountering a different subset of communities than I am, maybe you've been lucky, maybe I'm simply dead wrong, but getting Elm-maintainer-style passive aggressive over somebody pointing out logical flaws in the underlying claim as to why the heuristic is 'proven correct' is a rather unfortunate way to respond to what was written as constructive criticism of said logic.