How is OJ Simpson able to live with the fact that he *ALLEGEDLY* butchered two people?

Sociopaths rarely feel guilty for harming other people.

Some straight men who abuse or kill their intimate partners think they were within their rights to do so. They think it's perfectly okay to punish a woman who displeases them, physically, verbally, or financially, and if she tries to leave him to escape his abuse, they think they're within their rights to kill her. Because she "broke his heart", and his feelings are the only ones that matter!

I don't know where this belief comes from, at least I don't know where it comes from in the western world, but I think the odds are good that OJ felt that way about Nicole. He thought of her as a prized possession, not a human with rights of her own, and thought he had every right to kill her for leaving him and trying to find a new man.

I have NO idea how such a man explains his beliefs to the children of the woman he killed.

He has convinced himself that it was their fault for driving him into a blind rage.

It's simple; for OJ it's all about OJ. He's the COOLEST guy in the universe. ALL the adulation and praise MUST fall upon OJ and NOBODY ELSE.
Before the slaughter in 1994 OJ was LOSING. He lost his wife. He lost his girlfriend. Heck, he lost BEING OJ as Marcus Allen and other younger football stars were getting MORE ATTENTION.
So, what did OJ do? OJ got ALL THE ATTENTION back on OJ and it has been that way ever since. He can't live without it.

He's likely convinced himself that the deserved what they got.

By knowing the truth

It was not OJ. It was some Puerto Rican guy.

I have a friend who works in sports-talk radio, and he gave me the best explanation regarding the OP’s question I’ve ever heard. He said (and I’m paraphrasing):

“O.J. Simpson is an elite athlete, and like many elite athletes, he sees everything in b&w. Not black as in race, but in certainty. You either win, or you lose, and elite athletes are born and bred to win. Simpson saw Nicole’s being with other men as something that needed to be punished. After all, in his mind, she belonged to him. Killing her was a win. Getting away with it was a win. It’s all b&w to him.”

I would urge anyone who is any doubt about OJ’s guilt to track down the interview he did with Ruby Wax when he was plugging that vile book he wrote. His attitude towards the murders wasn’t just casual and cold, it was jovial! There’s a scene where he mock attacks Ruby with a knife that’s one of the most disturbing thing you’re likely to see.

He is the archetypal sociopath.