It’s been discussed in a few of the podcasts that maybe Doc and Marty might really have altered the timeline in a pretty selfish way and that Biff really got a bit of a raw deal.
If ever you see the actor who played Biff (Tom Wilson) I probably wouldn’t ask him about it as he’s clearly tired of the questions 
P.S. Apologies if this has already been posted. I had a look but I could’nt see it anywhere.
