In my opinion these are some of the reasons for the .22 shortage...
2012- remember that? Lots of people worldwide believed there was going to be some kind of apocalyptic event that would cripple the world as we know it.
Zombie apocalypse- same as above, but there's no date set for when it's supposed to happen
USA election results- Anti's elected into power and threatening to ban firearms , except for grandfathered situations. People would then panic buy so they could be considered "grandfathered"
Preppers- mostly these are the same as the zombie apocalypse types, they fill one sea-can after another, burying them underground in case of any of the above reasons.
Long gun registration- since we got rid of the lgr CFSC classes have been full, everyone wants to have a licence and firearms, everybody wants to play with semi-auto but can't afford centerfire . Enter the .22 semi-auto and unlimited capacity mags, just one guy alone can easily blast thru 500 rds in an afternoon.
Luckily we seem to be at the end of this shortage because shelves accross the country are filling up. I recently picked up a case of cci 40gr mini-mags that were nonexistent just last year.