Could be to help manage an impending bank run? There are many patrons that were alarmed to hear that their money could be frozen without a court order or a charge, but for suspicion of involvement in a political protest.
In response they withdrew cash, there have been reports of empty ATMs around Ottawa.
I've not seen any lineups, and as most can only draw $1k per day, I doubt that adds up to anything the banks should worry about enough to shut it all down. This was more likely the result of a single point of failure failing.
They probably all use the same vendor (FIS) and that vendor had some issues. We had issues with the same vendor yesterday with our mobile deposit sites.
I know CIBC uses FIS products, and i seem to remember some of the other ones being discussed (former FIS employee here)
Truckers found the network cable?
Government found the network cable
Exchange most of your money for physical assets worth owning and you will likely not have any problems.
Depreciation
Cash has been depreciating faster than even used cars.