When you let in the people who vote for Sanders you lost it.
When Sanders ran for mayor of Burlington he sued to get the kids at UVM the right to vote in the state. These kids pay no taxes here, attend the university as out of state students, have their cars registered elsewhere etc, etc. The courts, of course, sided with Sanders and now the college kids have enough of an impact to sway the entire state.
I’m not saying that there are not a bunch of liberal hippies here but if it weren’t for the out of state kids voting then Vermont would be much more like New Hampshire politically.