The majority of voters in America are moderate, not far right or left. For all the candidates to support the person with the best chances of winning is called strategy. For you to claim that the DNC made that decision for each candidate is a conspiracy theory.
But they didn’t do ranked choice. So for most of the primary it was Clinton VS Sanders. So we don’t know who would’ve won in ranked choice if all the other candidates stayed in. We only know that Sanders didn’t get as many votes as Clinton.
https://en.m.wikipedia.org/wiki/2016_Democratic_Party_presidential_primaries