Tesla proved the EV market and made EVs sexy and cool, which is helping tip EVs into the mass market. Without Tesla you wouldn't see BMW, Mercedes, VW, Nissan, etc. making mass market and luxury EVs. They'd be making no EVs at all or awful "compliance cars" designed to be undesirable. (The traditional auto industry is full of ICE heads and hates EVs. They have to be dragged kicking and screaming.)

If EVs weren't tipping we'd still be talking about how peak oil (the depletion of easy/cheap oil) means the end of modern transportation.

Tesla didn't make Musk a billionaire. The PayPal acquisition did that.

Does Tesla even still get subsidies? They got that DOE loan years ago but they paid it back and lots of other auto makers got government loans back then too. Or are you referring to EV tax credits? In that case those are also subsidizing Nissan, BMW, GM, and any other company selling a mass market EV.