It is very naïve to think that the availability of such tools isn't partly responsible for that intelligence; “We shape our tools and thereafter our tools shape us”. And it seems too man-centric of an excuse: you can see all our civilization being built on hands so you state that there can't be a way without.
The "they MIGHT be as intelligent, just lacking hands" theory can't have the same weight as "nah" in an honest mind seeing the overwhelming clues (yes, not proof, if that's what you want) against it. Again, same way that you can't disprove solipsism.