According to the movie's storyline why did The Texas Chainsaw Massacre killer Leatherface butcher people?

This is a difficult question but I'll give it a shot. well if you saw the Texas chainsaw massacre the beginning it explains more than any of the others in the series. The small town where the killers live their meat factory closes down for like unsanitary conditions so they start killing people and eating them. T.T.C.M. the beginning is more depressing and disturbing than scary. still worth watching.