A long time ago we believed Earth was the only planet, then we thought the sun was the only star, then we thought our solar system was the only system, and not too long ago, we though our galaxy was the only one. Now we say we live in a universe (one). Anyone see a pattern here?
What I find interesting if there are multiverses, is that every possible events, outcomes, thing has happened before and there is someone completely identical to you and someone else has also written word-to-word of shakespeare's hamlet