That, plus the fact that even when Vermont was in its last days of being “reliably Republican” it was in no way “Conservative” at least not if you go by the politicians it sent to Congress.
Lots of places in the Northeast, such as the Philly suburbs, used to be “reliably Republican” — but NEVER Conservative — and they went lurching leftward after the Republican Revolution of 1994 in which eeeevil Bible-thumping Southern Conservatives took over the party.
That's back in the days when the republicans were kept around just so the democrats had someone to run against and put a whipping on.
Plus the fact that a "republican" in the northeast was generally much more liberal than a democrat south of the Mason-Dixon line.