Bernie was still behind in delegates at that point, though he might have been picking up steam. He wasn't really ever a majority choice though: With the exception of Vermont and North Dakota, when he placed first in a primary it was with a plurality but not a majority of the vote. Collectively a majority seemed to be voting for a moderates, but the moderate vote was split among multiple people. When those other moderates dropped, that entire moderate majority coalesced around a single person. At least that's my interpretation when adding up % of voted by candidate.

However, I think a majority might not have wanted a moderate. They might have wanted a progressive, but voted moderate because their priority was to get Trump out, and they believed (maybe falsely, we'll probably never know for sure) that a more progressive candidate could beat Trump. The party establishment was certainly pushing that narrative.