The fundamental reason: the capacitive current of AC cables limits their transmission distance. This is for long-distance submarine projects, the transmission of large power is very difficult. Submarine DC cables have no capacitive current, transmission capacity is not limited by distance. So only a DC cable can be used to transmit power.
From the beginning of last year until now, the Russian-Ukrainian conflict, the Palestinian-Israeli conflict and so on broke out one after another. In these wars and conflicts, aerial cables, concentric cables, submarine cables and so on all play different degrees of important role.