None of the Dem candidates look like they're going to beat Trump in 2020. Biden malfunctions nearly every time he opens his mouth. Warren's momentum seems to have cooled. The progressives think she's a fake progressive compared to Bernie, and the moderates think she's still too far left and out of touch. The DNC and corporate media don't look like they'll ever endorse Sanders. Some media are trying to promote Buttigieg as their new darling, but he lacks substance, doesn't seem to appeal minorities, and the progressives won't go near him. Bloomberg would be an interesting candidate, but given the backlash against billionaires, I don't see Democrats embracing him enough to get the nomination.
The problem with the Dems is that the party's identity is split between moderates and progressives. The DNC hopes that hatred towards Trump will be enough to unite the party behind whichever candidate they can muster. Personally, I don't think that will do it.