The double-digit field is their way of trying to eliminate the upstarts. First, they place ringers at the various ideological poles to attract the fervent followers. That serves to eliminate the lesser pragmatic candidates. Then, they torpedo the ringer, with or without his cooperation (remember how Bernie just seemed to fold one day and we concluded he was bought off). If an upstart gets strong, they decide what losers to eliminate and everyone gangs up on the upstart.
Perez, a Hillary stooge, is working on the assumption that Hillary will have an uphill battle in 2020. Divide and conquer (with a double-digit field) is her only hope.
It makes it even more miraculous that Trump was able to survive such a bruising ordeal in 2016. But Republican voters decided not to have any of the establishment antics.
They seemed to have learned from the republicans. The splitter strategy that the republicans used in 2016 would be very effective for the democrats. Get a favorite son local candidates to run in all of the big states, (Cruz - Texas, Kashich - Ohio, Rubio - Florida) that can split the delegates up so that there is no clear winner, and the candidate must be picked (Jeb!) in the smokey back room by the establishment.
With the number of superdelegates the democrats use, it would work on the demo side.