So, in the beginning, there were no “boundaries” because that would imply something exist.

So if theres no boundaries, it means the “nothingness” is infinite.

So somewhere within this infinity, there would be a random event which causes the matter and antimatter to not cancel out completely.

BANG

Universe exist

Universe has random things happen

Galaxy

Solar system

Planets

Earth

Habitability

Life

Animals

Humans

Civilization

Here we are

🤷‍♂️

Edit: Non scientific, but, questioning existence is more of a philosophical question. Science probably would never answer it.