The many-worlds interpretation is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real, and that there is no wave function collapse.
This implies that all possible outcomes of quantum measurements are physically realized in some “world” or universe.
PBS Space Time playlist about many-worlds: https://www.youtube.com/watch?v=dzKWfw68M5U&list=PLsPUh22kYmNCAR1U8MD_1ELQnl640zYqi
The many worlds interpretation of QM doesn’t mean that EVERYTHING happens, only things that exist in superstition, so things that have a quantum state.