What's so weird about all of this is how strange and passive-aggressive it is.
If we're assuming that Russia did, in fact, do this: You're not going to cause any major long-term problem by cutting one power cable. It's just annoying. It's like China spraying water cannons and firing signal flares at "enemy" navy boats. It's like, "You better let me do what I want, or I'll bug you, and you'll have to put in some overtime repairing some minor stuff that I did! And you can't stop me!"
If you want to war, war. If you want to get with the program and stop killing Ukrainians, you can have your assets back and start to trade again. Don't try to tread this middle ground where you're showing the awesome might of the Russian military machine by assaulting an undersea cable, threatening to escalate to bombing trees and sabotaging all Finland's saltshakers if they don't start trembling before you.