I’ve been in meetings with him when he was still active at SpaceX and before he truly dove off the deep end. I had direct conversations with him telling him his engineers were wrong about something. He was quite intelligent and knew his shit. He was arrogant and a dick, but it was obvious he knew a LOT about the rockets he was building. He wasn’t doing the engineering, but he definitely understood the work going on.
Now, though, the dude is a fucking lunatic. I don’t know if he just started taking too many drugs or if the billions of dollars made something break in his mind or what, but he was not like this back then.