How exactly?
1) Prior to his nomination, few knew who Bernie was and what he stood for
2) The DNC's shenanigans made sure it remained this way
3) Hillbots would accuse anyone who supported Bernie of being sexist.
4) Donna Brazile came clean on this exact issue as well
They totally rigged it. It just was not a fair race. The DNC made sure of this. And with all the rigging, she still only got 3 million more votes.
And in poll after poll, Hillary beat Trump right within the margin of error.
Bernie beat Trump by like 10% in poll after poll. decisively outside any margin of error, and still to this day does. He just does not carry the baggage Clinton does.