You have to admit that he invested in some companies in fields that no-one was looking into. He's made a few big bets that have paid off extremely well. That's not nothing, and is impressive but it's not building a company. By all accounts he's a bit of a micro-manager, but I suspect there's only so much he could micro-manage or actually contribute directly in ventures like SpaceX or Tesla (he did make a door-handle patent tho).

Twitter on the other hand is another matter - no huge technical barriers stopping him from getting his hands dirty, no lives are at stake or regulatory bodies that are going to tell him "no that is dangerous" - so we're finally seeing what Elon unleashed looks like. So far it can probably be described as "chaotic" at best, it remains to be seen whether this chaos will disperse and Twitter will emerge leaner and better.

My belief is that he doesn't understand Twitter and its users quite as well as he thinks, and that Twitter will slowly get a bit more annoying and less profitable until he loses interest or gets distracted by something else. We will see, I use Twitter a lot so I hope that I'm wrong.