Because no one is buying the story that a quiet, 67 yr old retiree with millions of dollars and a penchant for gambling just snapped one day, drove 80 minutes with 23 guns to a Vegas hotel, and shot up a crowd of country music lovers. With no history of violence, no criminal record, no political or religious affiliations, no military background, and no love for guns even.

Esp. not his former neighbor:
http://thelibertarianadvisor.com/2017/10/03/neighbor-of-las-vegas-shooter-claims-he-didnt-do-it/