The universe very nearly did cancel itself out entirely. That’s why it is as empty as it is. The matter you see is the slight surplus there wasn’t enough antimatter to annihilate. Why this surplus? It’s one of the great remaining problems.

I think there’s an extreme form of the anthropogenic principle we can apply here. Universes may pop into existence constantly and destabilize into nothing because their physical laws aren’t fine tuned for stability, or because they don’t have an uneven amount of anti/matter. Perhaps universes are part of some extra-cosmic superstructure that’s just frothing like mad. Some bubbles last a little longer than others before they pop. We could be one of those. Perhaps the multiverse is a little bit of suds in some leviathan child’s bathtub.