I read an interesting analysis of all this recently. So they DNC changed the rules after Hillary lost. They were ‘sensitive’ to the charge that they rigged the primary against Bernie so they wanted to make the field appear more open. (I don’t actually know if they reformed their super delegate field or the proportional distribution of state delegates).
Anyway they changed the rules and now they have rules along the lines of “if you have $1 million in the campaign” and “if you are at 2% in the polls” and “if you can raise money from 150,000 donors in 20 states” etc. Things like that.
So this encouraged not only a bunch of people to jump in - it also encouraged them to chase the most outlandish and radical ideas. If you favor $1000 a month in guaranteed income, you can get 2% in the polls. If you favor single-payer health care, you can find 150,000 people to contribute $1. If you support reparations, or if you can look like you hate Trump more than any of the others, whatever it takes to qualify to make the next debate.
The candidates are spending something like $70 for every $1 they raise from small donors. Because all they are doing right now is coming up with crazy ideas in the effort to find those people who think Elvis is still alive to send them $1, so they can qualify for the next round.
Of course some of these candidates are looking for something other than winning the office of POTUS - book deals, senate seats, governorships, cabinet posts, tv programs, speaking tours etc. These rules enable that.
But this is a mess of their own creation, in response to the previous mess of their own creation. It does exemplify though the insanity in the way Demmocrats tend to manage things in general - the House, the large cities, the schools, the social programs...