We can relitigate this again & again. The pundit class said that Donald Trump stood no chance against Clinton, but the wave of populous sentiment pushed him past her. The same populous sentiment was behind Bernie as well. We will never know, but I think there is an argument both ways.
All I say is those who insist Bernie would have won are making shit up. The only way to know he would have won is if he'd've won. I remain unconvinced that Bernie's socialism would not have worked HARD against him.
The only reason I think he would've won is that a lot of main stream Dems were so turned off by DT that they would've pulled the lever for Bernie just to keep him out of office, & the populist movement that wanted to stick it to "the establishment" liked Bernie more than Trump. That was the swing.
As it was, people mostly voted Democrat to defeat Trump, or voted Republican to defeat Clinton. Would an equal number have voted Republican to defeat SANDERS?
I think a lot of Dems voted to keep Trump out of office. I think Trump voters voted for someone who "says it like it is", will "drain the swamp" or wasn't part of the establishment. Sanders had the same populist energy and messaging that Trump had & could've swung it. It's all conjecture though.
And don't forget that quite a few Trump voters were specifically rejecting Hillary! (Sure, some of them would have rejected Bernie too, but I doubt they would have been as numerous.) In elections where people vote for one candidate to defeat the other, the Republicans tend to have the edge...