The democratic party, up until 2016, used a system of "superdelegates": hand-picked people who had way more sway in choosing the party nomination. Sanders won the primary vote, but superdelegates widely picked Clinton. So, no, direct democracy was not an option in 2016.

After lots of complaints, the process was completely redesigned in 2018. Now, the candidate to get the majority of delegates becomes the party nomination.

Since Bernie has been clear as an actual candidate with potential to win, some democratic members have been caught speaking about returning to the superdelegate system [0].

Some believe Bloomberg's surprise entry in the race are an attempt to "crack the vote", that is, ensure that enough people vote for Bloomberg that Sanders does not win the majority, in which case the superdelegates are the tiebreakers to pick the nomination. This theory is very loosely backed up somewhat by an overheard phone call with John Kerry advocating him to join the race, to stop Sanders. [1]

[0] https://www.politico.com/news/2020/01/31/dnc-superdelegates-... [1] https://www.nbcnews.com/politics/2020-election/john-kerry-ov...