I expect there's a lot of firefighting and triage going on behind the scenes by engineers who are having to quickly come up to speed with systems they previously didn't work with very much, and I'm sure it's not great for their health, but mostly if things fail it'll be either temporary (for a few hours at most), or triaged inessential functionality.
My current perspective is he's going through a period in his life similar to the one Steve Jobs went through circa 1985, when his previous successes have gone to his head so much that he's over-estimated his own genius, forgotten the need to learn from other people, and let his demons have free rein.
In Steve Jobs' case, that led to his ouster from Apple and ~10 years in the wilderness. I think he matured a lot, developed a needed humility, and came to understand his own fallibility and limitations during that time. Ultimately, I believe his success upon returning to Apple was made possible by that earlier failure.
It's possible Elon will have a similar experience with Twitter. So far, I'm not impressed by his actions, seeing them from a distance. But I don't believe anyone can really be confident right now about how successful Twitter will be under his leadership, or whether Elon will learn the right lessons from failure should it fail.