Defense contracts are awarded extremely subjectively: there is very much an old boy network in play here. There are only a few primes. If you dig deeper into the "small businesses" that are awarded contracts, many / most are started by people already deeply involved in the defense space.

The Air Force has an initiative called Kessel Run [1] to embrace agile software development — that might be your best route to building better software for the DoD. I'm not sure if other branches have similar programs.

https://breakingdefense.com/2021/10/not-going-solo-air-force...