I was surprised when I saw Buttigieg withdraw before Super Tuesday, since he's doing respectably well in the delegate count, but now that I see both Buttigieg and Klobuchar withdraw ahead of Tuesday, I think there was probably a behind-the-scenes conversation in which the moderates agreed amongst themselves which was the most likely to win, and the others withdrew, so that the moderate vote would no longer be split.
I think they're trying to avoid playing into the narrative that I keep hearing from non-Democrats! on CF, that Sanders has already won the election and Democrats are trying to steal his prize away from him.
Yes, some of the "elite" party leaders were probably in on the behind-the-scenes conversation. But that would, after all, be leaders of a political party trying to guide their own party -- not an unreasonable action for a party leader.