It could be an entirely meaningless coincidence, the ship killing a bit of time, or doing some maintenance or a drill whilst out at sea in an area that happened to have a cable two miles below it, that is my option #1. It could be a bit of Russian research into whether they can find and disrupt these cables, that is option #2.
If we want to go down the fantasy route, and accept that the Russians would not just try to find a cable to see if they could, but would contemplate actually disrupting a cable, then that would adjust the ability of high frequency traders to play international stock markets, possibly allowing some kind of economic advantage to be taken somehow. In this fantasy, at some point in the future a cable mysteriously breaks due to a completely deniable cause, stock markets go into meltdown and someone in their Kremlin lair makes a lot of money. It is hard to describe the number of levels on which this fantasy makes no sense.