Now, who do you suppose would have been able to do that? These are extremely heavy and armored pipes sunk into the mud. You just can't drop a pressure cooker full of gunpowder on them. They have to be found by underwater cameras and metal detectors. Then the mine has to be nestled on top, with a shaped charge.
This is a great physics question in a land without physics. The lip-flappers can go on and on about it. Somebody was tired of all the lame excuses about broken equipment, and decided to do something a bit more certain.
Poots was musing about cutting off all energy exports and this is a great way to do it. No legal crap and lawsuits. They can go through the videos and find out whose ship was hanging out there after Poots blabbed. There will be no surprises, and it would take a full day to plant things. Then, everything will be denied.
ps. it has to be a pooty oly's monster ship. Those things have submarines pooping out of the bottom. The mines would be from their infinite WWII supplies, timed with mechanical clocks. The sats have direct coverage and can easily find out who did it, and the ship will be back safely in the loving arms of daddy.
pps. after many weeks, we haven't heard anything. They want to keep things calm, and the concept of weaponized mega-yachts is frightening.