I can't tell if the questions about why Sanders could beat Trump in 2020 when he lost to Clinton in the 2016 primary and then she lost to Trump in the 2016 general are serious or not. But assuming that they are serious, here are a few reasons off the top of my head where Bernie in 2020 clearly contrasts favorably with Clinton in 2016:
- Bernie is one of the most well-liked political figures in the country and one of the least disliked. The opposite was true of Hillary.
- Bernie has been perhaps the most consistent national political figure in terms of his politics over the course of decades. There's been remarkably little rhetorical or substantive policy flip-flopping that an opponent might exploit. Hillary was basically the opposite of that.
- Bernie's platform is clearly and very firmly grounded in his political consistency. There's no reason to distrust his platform or his commitment to it. Hillary faced the opposite problem.
I could go on. This is also to say nothing of things that may not have been directly in Clinton's "control," like Bernie's not being subject to an open federal investigation like Clinton was, Bernie not having a spouse whose presidency is now rightfully seen as disastrous for working people especially people of color, etc.
As to why Bernie lost the 2016 primary to Clinton, I listed a half-dozen or so reasons in my posts yesterday. On the most basic level, hopefully everyone understands that a primary is different from a general election, that 2020 is different than 2016, that starting from scratch in terms of national name recognition is different than having four years under your belt, and that the specific candidate match-ups in an election helps shape the outcome.
To be clear, there's no guarantee he would have won the 2016 general election, and there's no guarantee he'll win the 2020 general if he gets the nomination. But I like his chances, especially since the other front-runner, Joe Biden, is a walking ****ing disaster on nearly every conceivable level.