@
jackjjackson ?
We're not talking centrists alone here.
Moderate democrats make up a majority of the democratic party, if polling is to be believed. We're talking about people who don't post on Twitter, who are likely to identify as moderate or conservative, who might take issue with political correctness etc.
The more vocal more extreme face of the democratic party found online don't actually represent the majority, and you risk pushing a certain type of person away from the party with the more extreme takes on the left.
Trump has many issues that make him unfit for President; but he undoubtedly has a certain draw which might make him appear a desirable candidate over a self-consuming overly-woke left. It's not a scenario we can rule out, hence the need to appeal to moderates.