Boom Supersonic is entering the turbine engine market using private funding (they have received some limited government contracts and tax incentives). It seems like the free market is responding pretty well, although they still might fail.
https://aviationweek.com/air-transport/aircraft-propulsion/b...
That was my thought too. You can absolutely enter the industry, and big players do as the industry becomes profitable enough to sustain more competitors, it's just not available to the average person in the same way the average person can easily compete in the todo app industry.