> the electorate really doesn’t want immigration

Is that the case or is there just a significant minority that cares and the rest are happy enough as things are and would get mad if there was change - thus making their approach rational: get the votes of those who care but don't do anything because then you will be voted out next term.

I don't know myself, but this is something that I've wondered about a lot of issues that I care about where nothing happens. (I've long been on the side of more immigration)