He didn't do it, but he absolutely knows/knew what happened.
The fact that he didn't do it, is what gave him the confidence to be so brash to do interviews on CNN walking by the houses and explaining the case and also writing that book.
Other ppl who worked at that restaurant with Goldman had been killed previously, and the restaurant was shut down due to being a drug trafficking spot if I'm correct.
But OJ is not a professional killer who knew how to commit those type of murders swiftly, accurately and then bounce successfully