That division is much, much older. The beltway is full of people who benefit from corporations or come from wealthy families and are materially aligned against the working class, and their ideology reflects this. These people as a group stand to lose more from the democrats moving to the left and hurting the bourgeoisie than winning than staying in the middle and losing.

This is a common dynamic historically; liberals in power need the people to maintain power, but their interests aren't aligned with the people, so they pass policies that marginalize their own base of support, and so the conservatives take power and then do counterrevolution.