The supply chain is bled dry. Warehouses are empty. It comes off the production line and ships to their customers (distributors). Distributers handle their biggest customers first and the low-volume mom&pop shops are at the bottom of the priority list. When it finally hits the retail market, poof, it's sold and gone. It is amazing how efficient the internet is when everybody wants the same thing. Like a swarm of locusts on a farm field. Gone. Then people turn to reloading and buy all that equipment up (most of which will be for sale in the next five years).
I had been looking for SPP online for weeks. When I finally found them online, as soon as I checked out I looked back at the product page and they were all sold out. It took less than 5 minutes. A million people looking for the same item, all trying to buy it at the same time. Few get lucky, most don't. This then reinforces their resolve to 'buy it as soon as I see it' and furthers the panic. Just like the toilet paper shortage. Purchase quantity limits help to spread the available stock to more people. People complain about purchase limits. People complain about items being out of stock. You can't please everyone all the time.
Eventually people will calm down. Some, when they have enough quantity in their stock to feel comfortable. Some when they feel safe in the environment (political, etc). Some, when the thrill of it goes away. When this happens, there will be stacks of ammo and primers on the shelves on sale due to the excess capacity. I doubt all the ammo that is sold is actually being shot. Yes there are millions of new gun owners, but typically the new gun owners aren't quantity shooters and are satiated by a few boxes of ammo. I bet that the actual total number of rounds down range in 2020 is slightly more than 2019. Most of the ammo and components sold are in peoples' closets or basements.