Obviously she ran a bad campaign but the point is if Obama runs the same campaign you vote for him because he is likable
Obama's charisma did matter a lot. Unfortunately I don't see one candidate who has that "Obama cool" factor.
Obama was also not running against Trump. Say what you want about Trump, people "like" him for some reason. He's like a car crash on the side of the road, people stare. Plus I think he's just too good in a one on one mud slinging fight.
To beat Trump, you have to hit the issues that the GOP as a whole is weak on.