I agree for the most part there. Less so the founders, I think there sin runs more along the lines of being extremely naive (but in a way a lot of people might be, especially when the alternative might be to accept you're screwed).
> something must have gone fundamentally wrong much earlier. These levels of tension and distrust don't just arise out of nowhere.
Well, the tensions exist because they're being pushed for by large influences societally for political gain. The problem is they promoted a workplace environment where it was considered okay to bring it in, as well as to poke fun at clients (which is what kicked it all off).
I see this as an example of the cost of free doughnuts.[1] It's well known that we value the loss of something as more than the gain of something, and we value free things for far more than they're worth. Employees were given free reign for a long time in ways that weren't all that conducive to a diverse work environment or to respecting clients. Now they are being told not to do things that most work places already expect you to know enough not to do, either by explicitly telling you or by culture, such as don't blast your political views out to everyone, and don't be disrespectful to the clients, as that's where your paycheck comes from. My guess is the majority of people that leave if honestly reflecting on this in a few years would acknowledge that maybe announcing and focusing on your differences with those you need to spend time with is not as good a strategy for a happy and productive workplace as focusing on your similarities.
1: https://www.npr.org/sections/money/2012/07/13/156737801/the-...