like I said, I'm sure plenty of Sanders voters didnt come out for the GE but not because they thought Clinton and Trump were two sides of the same coin.Given turnout among young people, which is a large section of Bernie's support, was the lowest of any age demographic they either exist or his support is a lot smaller than people care to admit
They didn't come out because the Clinton campaign didn't energize them, if it did anything, it probably alienated them.
Personally, my friends who were Clinton supporters were very disparaging of Sanders after the primaries and before the GE.
Sanders ran an idealistic campaign that energized people that had never been interested in politics before. The Clinton campaign targeted all Sanders supporters as 'Bernie bros' and out of touch socialist idealists. After the primary she picked Kaine as her running mate and put very little effort in to undoing the pejorative message her supporters had proliferated during the primary. It's not a surprise that so many young people were disillusioned.
Now they have the likes of AOC.