The federal supply of N95s was depleted in 2009 during the H1N1 crisis. The federal government then used the funds directed toward replacing the supply, on other things. That is why those of us who work in hospitals and caring for Covid pts inside and outside of ICUs, were rationing these masks so that instead of one per pt encounter, we were only given one per day - or less in some places, by report. (I felt fortunate I could get a clean one every shift, for sure, but taking them off after coming out of a Covid room, and reapplying them over and over, were our unfortunate realities.)
That's when people decided to be innovative about replenishing supplies. As a subsequent poster mentioned, materials for the N95 weren't always available. Then we had competition in buying what little supply was available from virtually every country in the world! You'll probably remember our state had an innovative way of procuring masks for us using the NE Patriots plane to go over to China to get some. And of course we had some supplies confiscated at the NY harbor. It got to the point of being crazy. Where we are they decided to try to clean dirty masks, and a lot us in hospitals were sickened from the chemical smells left over. You think it's bad trying to wear a cloth mask in the supermarket, try wearing a very tight fitting one that has a strong chemical smell and is making your woozy and causing headaches while trying go take care of very sick patients. Not fun!
But this is what happened to the N95s. The same hoarding we saw with toilet paper and hand sanitizer, we saw with them. All over the world.