A normal relationship would be that you have 5 people who make guns who all show their gun to the army and the army picks the best gun. Instead the army has the 5 companies "propose" a gun, and they choose who gets to TRY To make that gun. And if they fail its sunk cost fallacy all the way down. Also part of why they choose a company to try and make that gun is because they always choose that company and they have the most "experience".
The argument for this state of affairs is that the military industry can no longer be spun up on demand and basically needs to be subsidized so it can continue exist in peace time. The reality is that these industries fuel continual low level conflicts, waste massive amounts of money and destroy the country.
The only real solve is that the they need a new branch of the military that handles production and R&D in house, and also mans and owns the factories, and to stop giving contracts to parasitic companies.