In Aquaman we got to see the introduction of Black Manta and saw the birth of his vendetta against Jason Momoa’s Aquaman, but we didn’t really get to know the character much beyond that. He was just on a quest for revenge the whole film, but we don’t know too much about his past, who he is or what drives him beyond that, at least as far as film canon is concerned.
Article source: https://www.cinemablend.com/news/2486367/why-aquamans-black-manta-is-excited-for-the-sequel