Whoever was behind 9/11–and I mean planting the explosives in the buildings–had to have been extremely well funded and organized, and they needed support within at least elements of the US government to conceal their involvement, and indeed the very presence of the explosives. It seems likely this would imply a government level involvement. I have said all along the Saudis would be one obvious candidate. They feared Iraq, too, as indeed they fear Iran, and have pushed for war, by us, with Iran, for them, just as they pushed for war with Syria, also for them, and their jihadists, although both Al Queda and ISIS are at least outwardly too radical even for them.
There can be NO DOUBT, none, that the full story of 9/11 is not in the public domain. People literally got away with mass murder, and concealed the fact of their crime, so there was never even a serious, credible investigation.
One hopes our system remains sufficiently robust and honest that at long last at least these redacted facts about the Saudis can be shared with the people our government exists in theory to protect.