If Vlad was stupid enough to blow up both Nordstream 1 & 2, this may be NATO's response courtesy of ATACMS sent to Ukraine in the immediate aftermath. Otherwise, if it was the domestic Ukrainian Hrim-2 it's not obvious why the Ukrainians wouldn't do it until now.
Think the boat and lorry bomb theories are far-fetched as the evidence on the road bridge spans appears (happy to be told why I'm wrong) to point to two detonations, and again why wait until now if the Ukrainians always had that capacity?