It was mostly deranged progressives angry over the "rigged" primary. And it didn't hurt that Johnson was saying "I agree with Sanders 73% of the time" at every turn. There are a few #NeverTrump votes mixed in too, but most of those people either held their nose for Clinton or proved to have no spine by the end and voted Trump anyway.
Wulfric/ Dwarven Dragon:
Although I agree with your general position that in the "Left Coast" of America that there was a significant defection to the Left (Bernie Write-Ins/ Greens/ Libertarian voters).... for example something like 12-14% of Oregonians essentially went 3rd Party/ Write-Ins.....I'm still not totally bought on the argument about how states in the Upper Midwest/ New England/ Pennsylvania voted in terms of minor party candidates.
Places like Utah and Idaho are obvious exceptions....
Honestly, I would like to see some numbers from the Midwest/South/Central Atlantic/New England states before jumping to a conclusion mat...
Not so sure about your statement regarding the Johnson/Sanders overlap, although certainly I had some Millennials in my family that were talking about going that direction.
Almost seems like you're trying to call out Sanders supporters for Clinton losing, even though based on many of your posts and the mutual threads from back in the '16 primaries that we both posted on, I don't believe that to be the case.