When you think of these managers, you need to ask, who are they? Where are they from? How did they get the job? What did they do before (large/small org)? What is their social background? What is their style?
At the root, I suspect it's shitty leadership at the top. The Valley execs I have met, let's just say they are not the sort of guys you would willingly go into battle for. Tech lacks a real officer class that commands respect.
I have also yet to see a non-white person quit over company culture issues. Thar be some elephants in thar rooms.