Global south cares for Russia as much as Russia is paying (giving discounts) anyone to care for it, not a barrel of oil more.

The most obvious reason here is simply mobster style intimidation. I.e. "You are helping Ukraine? We'll get back at you by damaging cables and what not".

I'd say the proper response to such incidents is to increase military help for Ukraine and blockade / confiscate / sink Russian ships wherever they do this stuff. Ships which engage in that should be treated as hostile military vessels.