Because half the Dem part is running for president. The circular firing squad has begun.
They are running because they think that it will afford them a degree of immunity from prosecution. If charges by Trump's DOJ are filed while they in the midst of a political campaign then they can spin it as a tyrannical abuse of power. But if timed so that the indictments fall after the primaries then.. There Can Be Only One. Over the next year or so they're all going to be ~~chopping each other's heads off~~ politically assassinating each other to absorb the fallen's ~~immortality~~ immunity like Highlander.