Yi Peng 3 crossed both cables C-Lion 1 and BSC at times matching when they broke

October 2023 there was similar incident where Chinese cargo ship cut Balticonnector cable and EE-S1 cable. Chip named 'Newnew Polar Bear' under Chinese flag and Chinese company Hainan Xin Xin Yang Shipping Co, Ltd. (aka Torgmoll) with CEO named Yelena V. Maksimova, drags anchor in the seabed cutting cables. Chinese investigation claims storm was the reason, but there was no storm, just normal windy autumn weather. The ship just lowered one anchor and dragged it with engines running long time across the seabed until the anchor broke.

These things happen sometimes, ship anchors sometimes damage cables, but not this often and without serious problems in the ship. Russians are attempting plausible deniability.

What are some concrete reasons why someone would want to damage these cables? Who benefits?

Russia wants to end NATO without going to war with NATO.

NATO's political unity and ability to respond is tested with these attacks. Russia does them one after another gradually escalating. Russia maintains plausible deniability or does so small operations that they can always walk them back.

Eventually, some country invokes Article 4 or 5 consultations. Russia hopes that US, Hungary, or Germany waters down NATO response. The conflict continues, but between individual countries not under NATO. NATOs as a organization may continue, but raison d'être is gone.

Russia and these NATO countries being probed are like the two siblings in the back seat. Mom, he's touching me. Stop touching your brother. Mom, he's holding his finger right next to me. Dad eventually says, don't make me pull this car over and start a global thermonuclear war

Except its always Russia instigating. We never sent someone to look at the spire of Saint Basil (the pathetic excuse offered for explaining the presence of GRU officers in Salisbury carrying out chemical warfare), or really struck at their weak points.

Are you actually saying the US has never engaged in propaganda within another country or attempted to influence the outcomes of their elections or influence their populace to rise up against their leaders?

You cannot be serious with that kind of belief

But of a jump from that to spraying poison all over the place.

Not really sure what you're referring. The US has most definitely sprayed poison all over the place in South America with cocoa plant eradication efforts. Or Agent Orange in South East Asia.

If you mean poison as in disinformation, then you'd be wrong there as well. We literally "bombed" Iraq with pamphlets from airplanes encouraging them to rise up against Suddam and we'd be there to support them; we didn't.