It’s hard to tell just what systems are communicating with other systems on which ports.

A variant on Hayek's Problem of Knowledge.  When authoritarian or totalitarian systems seek to impose on complex dynamic systems, you almost always have unintended consequences.  From Russia Cracks Down On VPNs, Brings Down Banks by Lawrence Person.

Here’s another example of the “new” Russia acting a whole lot like the old Soviet Union. Mere individuals will not be allowed to keep secrets from the glorious state, comrade.

But the Soviet Union barely lasted into the Internet age. Its communications infrastructure was built from the ground-up to spy on citizens, with entire floors dedicated to KGB agents constructed above telephone exchanges. It’s quite a different task to try to tap today’s vast array of encrypted digital communication channels. Ordinary companies frequently have a tough time locking down their own digital infrastructure, because it’s hard to tell just what systems are communicating with other systems on which ports.

Now scale up the problem to an entire nation that’s been cut out of the world financial system for waging an illegal war of territorial aggression, and a tyrannical government blocking vast swathes of what Internet is left in the name of information control like Hans Gruber’s minion chainsawing through the Nakatomi Tower’s trunk cables in Die Hard. All sorts of things you want to keep working are going to break.

I also suspect the attempt to be a futile one, at least for VPN users. I suspect the technical minds behind those are far more adept than the government censors trying to block them.