Having made a successful movie, but making the mistake of chopping off one of the iconic villain's arms at the end of it, a prequel was nearly inevitable. The problem with prequels, as everyone well knows, is that they lack tension. We already know how this has to turn out: all of the Hewitts survive and all of the kids die. Any other way and the original remake can't happen. From there, it's just a process of getting from point A to point B.
Along the way, as I mentioned, the film spends an inordinate amount of time explaining every little thing about the remake. Who really needed to see that Hoyt killed the original sheriff and took his car? That was strongly implied in the remake. Who cares that he lost his teeth fighting with a victim, or that Leatherface cut off the old man's legs, or the fact that Leatherface simply grabbed a chainsaw inexplicably sitting on a desk at the slaughterhouse. None of this stuff matters. How about answering why the rest of the family goes along with Hoyt when he suddenly starts serving them people meat? Why does his mother not care that her son ordered Leatherface to chop off her brother's legs? Why is she so damaged that she accepts all this?
The only real explanation for the family offered is that the meat packing plant closed and all of the jobs in town dried up. For some reason, this pushes both Leatherface and Hoyt over the edge into cannibalism. That seems a tad extreme to me, but I'm not from Texas.