Except - Paddock was touted as not being mentally ill by his family members n those who knew him, so that rule of thumb is not one that applies here
It also would not apply with the 911 theories bc the 911 theories include a deathbed admission, but only years after the theories began and the "evidence" of those theories have more to do with science than anything else - other supposed evidence are files, videotapes, and survivors that happened to be in specific areas at certain times.

Evidence regarding Paddock consists of science, videotape released from several different people at the shooting, sounds heard during the shooting, facts given by friends n family of Stephen Paddock, the fact there are so many security cameras - but none picked up any guns, the fact so many cases of ammo was taken up 52 flights but again no suspicion raised, the idea one person can change out so many guns n aim so accurately while firing so quickly from a far range - these are some of the things that helped me come to my conclusion before I ever heard any theories at all.