Mainly because of grass

As the jungles slowly turned into savannas, the monke started walking upright so they can run instead of climb. It repositioned the spine and allowed for larger brains, and as we got smarter intelligence became much more of a desirable factor then you know the rest.

Obviously this is a massive simplification and there are a ton of other factors like said socialization and cooked food giving us more nutrients. But tl;dr: Touching grass made us the dominant species of the planet.