The capital composition of the US military industrial complex has evolved quite a lot since its birth during the preparation for WWII and the primary industries involved that produced basic high use materiel like artillery shells and bullets had to diversify and switch operations to other commodities, primarily more high tech (although not necessarily useful or quality tech), less quantity, higher price stuff because they'd go bust after the stockpiles and quotas for shells etc were full.
If anyone did an economic history of US MIC companies there would be a lot of merges and repurposing of the old shell factories etc since they're very useful for long term combat in land warfare, not so much for just restocking a standing army that uses some in exercises.
Basically you have vampiric companies diversifying outside the war economy context that created them so there's no need for industrial scale production on a war economy level and they switch to producing far fewer but more Gucci missile systems and components.