If we consider other hominids, we don't know exactly, but it seems we outcompeted them. If we consider more distant animals, because we converted the entire planet to provide for us much faster than they could evolve to catch up with us.
So it might be more like "we are the ones that remain", but yeah, either variant is a spin on the old weak anthropic principle, which is never quite satisfying.
> fire-cooking, rock-throwing domesticating niche
Just knowing if that was the evolutionary pressure along the path would be enough for me (even if it could have been another ape or a corvid or whatever - or maybe they are on that path now?)
BTW Matt Ridley has the theory that division of labour (trade enabling specialization) was the gradient.