Face it, LHO was not a lone nut assassin. You have to be lost in the weeds to think otherwise. He may have been heavily involved, but not a lone nut. The LN narrative is a house of cards that only requires 1 breach of logic to topple it and it's far more likely that the JFK assassination was part of a carefully planned conspiracy than an ex-military/singleton agent/commie happened to get a job at the TSBD 3 weeks before the re-routed presidential motorcade made a sharp turn onto Elm and served up JFK on a silver platter.
You could ask Oswald's doppelganger, Thomas Arthur Vallee the same question a year before in Chicago.
https://riversong.wordpress.com/jfk-assassination-plan-a/Face it, this was most likely a conspiracy, in which case LHO's best defense against being a LN is that he was a patsy. This conspiracy needed a patsy and LHO was the Vallee of Dallas. Sure, there was a shooter(s) up on the 6th floor but they certainly weren't relying on Oswald firing a mannlicher carcano to do the job. The MC had already been planted by that point and maybe someone took some token shots with a Mauser because shots must be heard coming from the 6th floor to set up the patsy. But Oswald himself never took any shots because he never fired the MC before, otherwise, he would have sighted in the scope and his prints would have been all over the MC like stink on a monkey.
He did not have the time to wipe down the rifle. Check and mate.