These are propaganda coups for the Russians. They’re dragging anchors and getting away with it.
Can’t EU countries block Russian vessels navigating the Baltic sea?
To access the Baltic sea from the North sea any ship must cross the Danish straits. Same question.
It gives the impression they’re winning and makes the EU and NATO look weak.
Place sea mines defending the cables. Post maps for civilian ships to keep out of the mine zones. Anyone goes near the cables anyway? Well, you were warned.