And they will likely go broke - the failure rate of startups is high, on top of that when something is politically popular snakes come out wanting taxpayer money and selling shady investments.
At least ZeroAvia has flown something, whereas Arion supersonic did not even have a prototype - it has folded. (Boom Supersonic in contrast built a serious demonstrator aircraft that should fly ‘any day now’ as software people like its co-founder are wont to say. And Boom is flying its pilot vision system already, in a small airplane.)