I’m curious to know why it happened only today. Was it some new sanctions? Were they slow to apply existing restrictions? Does it have anything to do with official sanctions at all?

There were reports mostly from southwestern regions, near Ukrainian territories.

My guess is that the same subnets are shared between those regions of Russia and occupied territories of Ukraine.

Conspiracy theory: the decision to add the entirety of Russian IPs to the blacklist was made on a whim by some ground-level technicians, and the management will either apologize, call it a misconfiguration and revert the changes, or simply allow this to go through and invent some explanations for the public later, depending on how much they even care. /conspiracy theory