He was always insane, it just wasn't as public. I'd back that up with this 2018 Wired piece: https://www.wired.com/story/elon-musk-tesla-life-inside-giga...

Ignoring everything else, if a manager at your company has coined a term like "Elon’s rage firings", I don't think there's a need to know anything else about the work environment.

I'd say Tesla/SpaceX achieve cool things not because of him, but despite of him.