I’ve always felt that the reason for all the suppression that opened up so many conspiracy theories had more to do with the “how,” rather than the who. As Oswald had access to the CIA for a time, I wonder if he used a prototype semi-automatic and the bolt action was planted to cover up the Agency’s mistake.
All the answers are available if you’re willing to read, it’s not very complicated what happened, we have the rifle, we have the killer, we know where he shot from.
A bolt can be worked plenty fast enough to do what was done. As an ex-Marine, I’m sure he could run that bolt nearly as fast as a semi.