I don't know it seems plausible to me that it was just an accident. There is plenty of legitimate Russian activity in that area. I'm no fisherman so someone correct me if I am wrong, but I don't think it is that unusual for them to go back and forth. It's not surprising that it happened to a vulnerable spot, because if it wasn't vulnerable the cable wouldn't have broke and no one would be looking into it. Finally the Russians have submarines they could use to cut the cable without being detected. Who runs a covert op with AIS on?