Is Elon Musk does enough to call as legit and have a good reputation? then in that case Bitcoin is legit as he once mentioned it before on his tweeter and he's now venturing with it along with a couple of large institutions. Besides, there's a lot of people who can be called living proof as they use Bitcoin on their investment and different legit transactions. If it is fake it wouldn't survive for too long and institutions will not waste their time and money on it.