There are other factors involved in military R&D and other decisions. There still massive and cut-throat “turf wars” that the U.S. Military services engage in and shape the R&D and operational decisions by the Politicians. For example, after WW II, the newly created USAF worked very hard with their supporters in Congress to disband the U.S. Navy because the USAF had the Atomic bomb and there was no use for the Navy, and Congress could save all the Navy’s funding (or give it to the new USAF instead). A portion of the USAF, know as the “Fighter Mafia” has tried to get rid of the A-10 Warthog because it was designed to support the U.S. Army. The U.S. Army has been trying to gain control of the USMC or to absorb it since WW II ended. We’ve all seen how those “turf wars” ended. And the “turf wars” continue to this day!
One further note for those of you who think they aren’t still being fought behind closed doors. In the late 1980s I worked with USAF, USA, and USN reps to create an aircraft engine Joint Engine Specification because each service had their own unique engine specification for the same basic engine. We met for about two weeks, but failed because the AirForce and Army reps couldn’t stop arguing about how the Army violated the “1948 Keywest Accords,” that basically divided air responsibilities between the USAF and the USA, when the Army put weapons on Helicopters!
This reality continues to determine what is researched and funded.