Honestly, they don't really need to prove malicious intent. The stakeholders of the cable should hold the ship owner liable for the cost of repairs, holding the ship captive as collateral until such a time comes that the amount is paid. If the cost can't be paid, then confiscate the ship and sell it to recoup the cost and as a deterrent measure.
Whether or not they did it intentionally and why is a matter that should be left to intelligence agencies who will interrogate the crew and collect information about the ship to understand what's going on and act accordingly.
Man, it's days like this i feel bad for not paying my taxes in Ireland. What an exemplary attitude. I wish Israel left my country too. Europe should all be making Israel unwelcome, not cozy up to them.
We've had enough genocidal, ethnic cleansing, mass murder, racist regimes.