Like most things, the answer is somewhat complicated (as in numerous factors). One of the biggest, is that many people obtained licenses and firearms in both the USA (much bigger population, much bigger effect on supply chain) and Canada. Along with their newly acquired firearms they bought a few boxes of ammo. This alone (but isn't the only factor) created a huge surge in demand for ammo. Ammo production was previously at a level that was intended to be somewhat stable with the prevalent demand for ammo prior to the surge. While the demand could escalate very quickly, production is slower to increase. Even when it is decided to increase production you need facility space, trained staff, supplies, and tooling. While trying to increase production the producers where faced with the unknowns and added complications from COVID (work place precautions, lock downs, availability of workers, supply shortages etc). Also, the same companies producing supplies for reloading are the ones producing supplies for making production ammunition. As the demand for factory ammo had increased significantly, so the demand on the limited supply of reloading components.
Here is a link to a video with the President of Federal, CCI, Speer, and Remington giving a better explanation than I have provided.
https://www.you tube.com/watch?v=KIgvoJKovIg
If you shop around, you can find a lot of components that seemed unavailable a few days before. Production rates are high and increasing. Many of the producers allow you to set up to receive an email when they have what you want in stock. Then you can follow the chain to a Canadian retailer for that product and make arrangements. A few companies even pulled product aside for me and I was able to specify the specific Canadian Distributor that'd would be ordering it to sell to me.
Like many things, if you put effort in, in an appropriate manner, over time, you should be able to see some results. Best of luck!
(I hope I have followed the Forum rules correctly in the manner of providing the link). You need to copy and post the link and delete the space between "you" and "tube".