There are many universes, and the universe we live in is just one of many universes. Because there was no universe before BIGBANG, at the moment of explosion, that is, at the singularity, there are countless possibilities for the combination of particles due to the principle of particle uncertainty, so the universe we are in is only one possibility.

I recommend reading Hawking's A Brief History of Time.

Stop! Don't scream if you don't understand upstairs.

Stop! Do you still exist? There is not much more than you in this world, and there is not much less than you!