I would also say that it is a product of the federal government in recent decades gradually losing its ability to keep people on staff (or pay them enough) to build the knowledge about how to run/build such projects themselves. And cost-effectively.

If you recall the earlier days of aerospace, aircraft, etc., technical experts in the military would basically tell Lockheed, whoever, exactly what they wanted to design, or would be equally qualified to set out the specs and be deep in the design.

Over the last decades, that capability (I believe) has largely left the government/public institutions. We have essentially outsourced the design and building of aircraft, spacecraft to private contractors, and when that happens it naturally costs more to do, to pay them to do that job (and take on the risk of doing it). After all, they are profit-seeking enterprises, while if that expertise had been kept in government, it would not be.

If you take it by examples, the era of WW2/shortly-post-WW2 military aircraft was when Air Force/Navy/Army aircraft engineers helped design planes that contractors would get marching orders to go build (of course with their input). Nowadays, we're in the era when Pentagon procurement office tells LM / Boeing to go design us a plane to these outcomes, which are cobbled together from 4 different branches of the military and uncoordinated generals' wish lists.

And we're surprised that a fighter program ends up costing $2T.