The Dem primaries were, in large part, arguments over policy and no faction or candidate (left/centrist) appeared to really stand out. IMO because this race was always going to be a referendum on Tweetie. The Biden campaign won while sticking to this strategy.The problem you'll see moving forward if Biden goes hard left (which thankfully he won't) is that he won't have the "anyone but Trump" factor influencing the turnout.
That's the reason the "left" did well here - the more left you are, the more enthused you were to go out and vote against Trump. But what happens when Trump isn't a factor?
Basically nobody voted for Biden. Hence the wild celebrations when he won that were basically all about laughing directly at Trump.
Now he gets the chance to prove he's governing for the whole of the country with actual policy geared toward that end. We shall see. I certainly have more hope he will than I did with the last guy.