Back to the future 3 should not have happened

This isn't one of those there's 3 deloreans in 1885 or something like that. No this is much simpler, as marty could have listened to doc and just stayed in 1985 instead of time traveling to 1885

Sure he did he got by mad dogg tanen but that would have changed nothing well almost nothing as marty is already in 1985 with the present that he wanted. The only difference is that doc brown would be dead

That's probably why he went back in time although the 1955 doc could have sent himself foward in time after he help's marty in the past and tada another doc

The trilogy has a lot of time travel that makes your head hurt