For all of the possible suspects (mainly Russia or the USA - but maybe rogue state elements or client states) the negatives of this act seem to outweigh the positives.

The gas that has bubbled out of the Baltic is Russian owned. The pipes were not moving any gas (Nordstream 2 never did; Nordstream 1 shut down by the Russians a month ago to put economic counter pressure on Germany and the EU). The sabotage may make the pipes unusable in the future (salt water damage) and so prevent future Russian gas sales to Europe. There is no short term or medium term economic or political benefit to anyone - but as a warning to someone (!) and an escalation of the conflict it could be huge.

If the Russians blew the pipes they are becoming even more irrational and self harming.

If the USA (or Israel or some other state or agency working for them) did it, that is even more worrying and sinister.