Sure, you can join something like that, too. That's not the important part. The important part is to get a sustainable business out of it. Just 5 years ago nobody believed this was doable.
Well, clearly the _actual_ founders of Tesla did...
5 years ago they weren’t there anymore. And Musk famously slept in the office and nearly went bankrupt and insane trying to ramp up production of model 3.
When Musk joined the company was barely more than an idea and he joined 7 months after it was incorporated.