My mom pretty much had an existential crisis over this when she made a friend at work and her husband turned out to be Trump supporter. And this is in Canada. It makes you wonder where girls like that even find guys like that.
Like the 'Thin Blue Line Coward's Swastika', it's really not exclusive to a single country. It just means they have fascist beliefs, are probably racist, and want others to know!
There's no limit to who will fall prey to their particular algorithms and confirm their particular biases. Mix that in with an identity rooted in the bigotry and biases they inherit from their parents.
When you've been conditioned all your life by society (and conservatives) to believe that your primary function is to be a baby factory, and you know you only have a finite amount of time to be a baby factory before you're old and busted and cast aside, you do whatever you can to land someone stable enough to marry, regardless of their politics.
This is going to come as a shock to some folks but people don't need to have the same politics to get along.
My wife is more conservative than me. We don't spend much time talking about politics and avoid being dicks to each other. When elections roll around we go to the polls and I'm sure cancel out each other's votes for a bunch of candidates.
When you and another person believe that there's more to life than politics it's easy to not get hung up on them when it comes to personal relationships. When you or the other person allow politics to dominate your life it isn't.