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.