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?

When Trump becomes President next year he is expected to demand that Ukraine settle the war with Russia or risk losing US aid and military support. It is why Russia is throwing everything at re-taking Kursk and US is now allowing long range strikes.

If the EU decides to join the US the war is over and Russia will keep the occupied lands. If the EU decides to support Ukraine then because of the devastating sanctions there is a strong chance Russia loses.

So it's in Russia's interest to make life as difficult as possible for Europe over the coming months in order to convince them that ending the war is in their best interest.

The USA, UK and France approving the use of the long-range missiles was described as a response to Russia using North Korean soldiers.

A fair point, but described by who?

And was this just a post-hoc justification, or had the western powers declared that they would retaliate if Russia involved other armies?

In any case, surely the 'punishment' should be directed at North Korea?