Elon started out thinking he could work with these people, and then as he prepared to join the board, rapidly became disillusioned, and became convinced that they had no idea what was good for Twitter and the only exec who ever did was Jack. I would recommend looking at some of the text exchanges between Elon and Parag/Jack, they've been published and talked about pretty much everywhere, if you want to understand the vibe shift that basically guaranteed this would be his first act.