There are many practical political reasons for why Republicans act as they do but the root driver is fear.
Pretend for a moment that you died psychically as a child, that you did something so terrible that your guardians threatened not to love you, not to take care of you and keep you alive and they showed you what that would look like. You would do anything not to let that happen, anything to pretend to obey including abandoning all hope of spontaneous self expression and being joy happiness. We died psychically as children with varying degrees of severity, of course. Some of us are condemned to turn out as monsters while others highly adaptive and capable of great worldly success, but all scarred by the experience.
What is fear, then, but the suppression of any memory arising of this, any self awareness that we are in various degrees psychically dead. And what is the obvious result, the suppression of all negative feelings of self pity and self love least the traumatic events happen all over again. So fear is when threat of awakening to what we really fear presents itself, a maximum effort to suppress all feelings which is the equivalent of death. We fear knowing we are dead, that we died in childhood.
And where does that leave us, those who had it really bad? It leaves us with the need to be in control, to prevent anything that would shake us to wake up, to disturb our precious sleep. This is what lies at the root of the authoritarian mind, right or left, the fear of loss of control and the need to make others conform to our personal world view.
And, of course, because any herd of authoritarians will always have minor deviations of opinion, the greater the success of the elimination of the threat or the less successful it becomes, there will be internal schisms and recriminations and blame. Authoritarians will always eat themselves because fear is always projected.
You can be sure that the only person who is really right in this world is me and to prove it I will gladly support your elimination. Please don't ask me to feel again my own original psychic death. No way I'm allowing that. Sorry.