Bipedality in humans may have resulted from the advantage gained through the higher vantage point and ability to see longer distances.
This makes sense on the African savannah, but not so much in the forest which is supposed to be Bigfoot's primary habitat. In a forest, there's nearly as much still over your head when you're standing as there is when you're on all fours, so the advantage of bipedality is considerably less. It might improve your ability to see over the bushes interspersed around the trees. Perhaps this is the reason Bigfoot is much taller than humans, in order to gain the maximum advantage from bipedality in a forest environment, but I still imagine that the gains might not be worth the other physiological and behavioral trade-offs.
Another possibility would be that Bigfoot developed bipedality in a previous habitat, prior to migrating to North America. It is not known if Gigantopithecus, a possible ancestor of Bigfoot, was bipedal or not, but bipedality would have indeed been more advantageous among the bamboo than in the forest.
Regarding tool use, it may be that the Bigfoot hand simply is not sufficient for tool use. In the image below of a possible Bigfoot handprint cast, the thumb appears to be relatively smaller than in humans, and in a position that might reduce its opposability. If that's the case, Bigfoot's hand just isn't ideal for tool use. Widespread tool use among early humans is one of the primary things that made further brain development advantageous, so if Bigfoot is still in a stage where its hand anatomy hinders tool use, then perhaps this is why Bigfoot doesn't display all of the characteristics of humanlike intelligence.
As an aside, the thumb in this hand cast is perhaps more reminiscent of a panda's "thumb." The panda's "thumb" aids in grasping bamboo, which is suspected to have been a dietary staple of Gigantopithecus as well.