Montana has had an late influx of liberals from the coastal states, and they've settled mostly in communities in the west of the state. Missoula is the best example. But in addition to that demographic, which isn't
huge, is a large proportion of Natives, old working-class traditions and little Mormons.
Montana's actually pretty populist. (Socially conservative)
Populism, apart from the fact that it isn't an ideology, is not entirely social conservatism and Montana is neither a populist nor a social conservative stronghold.