Bernie isn't going to win the 2020 primary - he has too much of a blind spot for racial and women's issues. AOC will support him anyway, because she supports his policies, if not the man himself. It's a voice that needs to exist in the modern Democratic party, and should always have a seat at the table. We aren't fighting just to stop the bleeding, we're trying to reattach the leg. If someone like Bernie makes someone as liberal as Warren more palatable, all the better.
Medicare for All is only on the table now because of progressives. AOC has also jumpstarted the conversation on taxes and student loan forgiveness. This is more important than playing pattycake with donors in a congressional session where we can only pass legislation by conceding legislation. She was in the trenches shaking hands with Republicans today. She's trying.