I dont know. Because there are many very good, polite devs. Unlike pretty much all other project there's no code of conduct or conduct norms. Something as simple as "be respectful", would be a big improvement. It's just a negative setup, compared with other FLOSS projects. I guess it's an experiment, in a way, too.
Discussion
A few bad apples, as iirc the saying goes then… I’m not involved in the dev community but I could imagine that a mixture of hyper-competitiveness and craftsman/artist‘s pride can bring out the worst in people. Thinking chefs in a gault millau kitchen and alike.
Yes, most of them dont even lift!