I suggest at you remember incorrectly. The DNC has no function is pushing any candidate, and nor are they able to do so.
The worst that is able to be said is that some members of the DNC favoured Hillary to win, but such was kept to internal discourse and only occurred prior to other candidates officially entering the race, or after Hillary was clearly going to win based on the nominated delegates.
The DNC have no mechanisms to influence the primaries. They don't control the State branches of the party, they don't control the Supers, they don't control the electors. They have nothing to do with funding during the primaries, not in advertising or campaign management.
Their job prior to the Convention is to file paperwork, which they did equally for both sides, even making sure that late submissions by Bernie's team didn't disqualify him from several ballots as it should have by law, and organising the Convention itself. It's not until after the convention that they are opened up to pushing their candidate and helping the primary winning campaign.
Bernie's big problems were nothing to do with the DNC, it was a failure to get his message to resonate with the mainstream Democrat voter. He also failed to woo the supers, even failing to send them materials when they requested it, but rather attacking them for their choosing someone that they knew well and who had been with the party for the vast majority of her life, over someone that they didn't know, whose campaign didn't seem that interested in getting them on his side, instead they spent far more time complaining about them which likely turned them off even more.