Also, I think they thought they didn't stand a chance, so limit it to where he could win one or two to make a statement.

Back to numbers crunching. If you check out the early Democratic primary results for 1992, you will see that Clinton was not winning anywhere except the South. But anywhere except the South was divided among several different winners. So Bill's southern sweep gave him a commanding lead over 2nd place despite having fewer delegates than his combined opponents.

Had 2016 replicated 1992, but with Sanders sweeping the non-South, Bernie would have had those delegates by himself. And thus the win.