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

So what would China's motivation be here?

Helping Russia

So what's the strategic importance of this move? inb4 "they're just acting like hoodlums to show off their strength".

Keeping Europe on edge and cowed, so that they spend less time and effort on Ukraine. This allows Russia to capture more of the historic Russian Empire in the east, which makes them more powerful and embarrasses the Western countries, pushing more unaligned countries into BRICS.

The endgame here is to build a new world order with Russia and China calling the shots (actually, China calling the shots, but we're not supposed to say that yet).

This seems very unrealistic, as the resulting distraction is probably of low consequence concerning Ukraine.

Not even replying to the claims about world domination, I don't have time for these... "suppositions".

Yes, and that's half the problem. The only ones taking this seriously are the Latvians, Estonians, and Lithuanians (although the Finns and Poles finally woke up to it last year - also why Poland upped its military spending to 5%). The Estonian military reports are particularly enlightening, and Timothy Snyder offers background into the why.