Nowadays, I think the main reason humans took off is because human hands were extremely suited for tool use and being at range, which means that there is a selection effect at both the genetic level for more general intelligence and a selection effect on cultures for more cultural learning, and animals just mostly lack this by default, meaning that their intelligence is way less relevant than their lack of good actuators for tool use.
Nowadays, I think the main reason humans took off is because human hands were extremely suited for tool use and being at range, which means that there is a selection effect at both the genetic level for more general intelligence and a selection effect on cultures for more cultural learning, and animals just mostly lack this by default, meaning that their intelligence is way less relevant than their lack of good actuators for tool use.