Weapons have a long shelf life (on the order of decades) and slow production but as long as that slow production exceeds peace time/training use you can build up a stockpile, they blew through that stockpile fighting a war they didn't need to fight and it turns out that "Throwing money at the problem" isn't enough to solve it quickly.

Maintaining industrial capacity to make a thing at a higher scale than you need to make it at currently isn't free, it costs money and so the companies simply don't.

Because all of the plants like this (https://en.wikipedia.org/wiki/Columbus_Castings) have been torn out.

Because they've used up all their complicated, expensive weapons obliterating middle eastern children

The Iran War was a war that even the military industrial complex had resisted starting for decades. This should tell you what a generally bad idea it was.

Normally, if such a war had been started anyway, it would have resulted in distributed adaption from the military / intelligence bureaucrats each working within their own constraints/incentives - a scaling of the aims to reflect prudent for scope/intensity/etc for an elective war.

But instead, the war is being prosecuted for maximalist aims by an aging con man. He was fundamentally incapable of understanding the concept of "no" - real constraints, difficulties, problems to be solved - even in his heyday of the 90's. Never mind the additional confusion that 30 years of neurological degeneration has wrought. Any sort of feed back or judgement from people experienced in topics is considered "woke", and so experts are sidelined in favor of yes men for Dear Leader.

And so rather than any dialing back of scale (or perhaps even planning ahead to defend expensive military assets sitting around like ducks), the "plans" are to just push ahead harder, commit harder, expend even more of our resources, etc - surely winning, and the validation that it carries, is merely weeks away. Similar exceptional entitlement is seen in supporters of the con man, who champion some idea that success can be assured if we merely have the will to take it - hence the constant discussions of the form "which crimes against humanity do we need to commit?"

Fundamentally, this is what happens when people foolishly elect autocrats - autocrats promise simplicity and expediency, but these qualities only exist in their own limited mind that cannot fathom the realities of situations. And so what autocrats actually bring is incompetence, inability to adapt, and ultimately ruin.

If the US and its military do recover from this, it will not be due to the simplistic cheering of the rash destructionists, regardless of how much "fresh energy" they bring. Rather it will be long, slow, boring work done by everyone else picking up the pieces after their catastrophic reign is over.

Because you guys live in a bubble