The Washington Post actually had an article about this back in March or so.

The issue that you have is that there is a decently large capital cost to building new production, and once the pandemic is over, the budget hawks are going to swoop in and cut purchasing of masks down to below pre-pandemic levels because there's now a massive unused pile of the stuff, why do we need any more? So the guaranteed-purchase contracts are abrogated, and the manufacturers are saddled with a lot of debt and no prospective income.

(This isn't a theoretical thought exercise, it actually happened during the H1N1 flu crisis).