They do it because they are in a war dealing with enemies.
When I made a very diplomatic plea on facebook for people to vote for Harris largely based on character, a high school acquaintance answered in firm opposition. She cited abortions and sex changes and proclaimed these things "Kingdom issues."
Years ago, I got a hint about this movement when I saw placard advertising a call to people to hear a guy known for leading a philosophy of holy warrior voters or something like that. Nothing about this on major news outlets. Now, someone has pulled it together.
Atlantic has a great article on the Christian Kingdom movement.
That's long but worth it. It's not the aggregate effect of many different preachers railing on about this stuff. It's organized and nationwide and possessed of the belief they are moved by God Himself.
When I was driving from Lakeway to Clarksville late in the evening of the 9/11 attacks, I wondered if there was anything we could have done to prevent the [ETA] will to attempt such an attack. I concluded not much because how can a person believing he is ordered by God do otherwise?
Sadly, it has wider application than I considered at the time.
I also decided that late night to never criticize religious hypocrisy; without it, religion is unbearable.