In another timeline, Joe Biden would have ran in 2016 and beat Trump in a landslide, and he would be the outgoing president in 2024 due to term limits and not being essentially forced out by his party.
there's also a timeline where Biden would have beat Trump in 2016, people would have generally been underwhelmed or unhappy for whatever reason, and Trump beats him in 2020 and is then re-elected in 2024 or becomes a dictator, whatever.
I like playing the timeline game too but assuming Biden would have won in 2016 and therefore had a happy smooth 8 years as president isn't necessarily a given. Things play out how they play out. We don't know what a 2016 Biden presidency would have looked like or the ripple effects.
It's kind of inevitable a guy like Trump would have become president at some point IMO. It was just a matter of the pot boiling over. Thankfully he left a bad enough taste in everybody's mouth I don't think he has a strong chance to be re-elected.