The Poseidon drone has an enormous payload capacity for megaton bombs and a 1 km diving capability - perfect for a cable cutter.
Russia would get a lot of utility by holding the submarine cables that the western world relies heavily for communications hostage. If the west threatens sanctions - cut some cable, and watch them soy sperg over billions of dollars per hour
in financial losses.
Best part is this vulnerability is entirely asymmetrical: Russia is not as reliant on underwater cables as the collective west does since it sits on the largest contiguous landmass on the planet. Cut some overland fiber optic cable and some dude in a van would be splicing that shit in an hour. Underwater cables under a km of water, not so much.
Its also almost entirely unfeasible to stop. There's not nearly enough hulls in the collective western navies that you can tail every Poseidon drone - and you can't even think about patrolling the thousands of kms of cables.
Lastly, physically turning off the internet should be one hell of a good card to play in trying to avert WW3. Bombers aren't nearly as useful as a signalling tool compared to literally pulling everyone off the matrix. That should at least get some people to think about their impending mortality and actually do something about it, like overthrowing their governments.