The DNC did suppress Sanders and showed massive bias towards Clinton, the email leaks showed it. Clinton's campaign got debate questions early. They got preferential treatment in the media. Then when Debbie Wasserman Schultz, the DNC chair at the time, was kicked out because the collusion became public knowledge, the Clinton campaign _immediately_ hired her. If there wasn't massive collusion, then there was at very least an image problem, which Clinton did nothing to help by hiring the very person forced to resign.

Also, the message sent by the two were not identical at all. Sure, if you tallied them all up and compared them by existence they would be very similar, but the difference was in the focus. Sanders' campaign focused on socioeconomic inequality which would have resonated more in rural America, while Clinton's campaign focused more on social issues, which matters more in the urban centers where the economy is less of an issue.