Optics.
Perhaps it is the plan to make DJT speaker of the house. The optics would not be as good if 45 opposed McCarthy because he wanted to be speaker of the house.
Now Trump can get a nomination without that fight against McCarthy.
After all, McCarthy is the first failed speaker vote in 100 years. We all know Trump's world consists of Longshots.
If he had supported anyone other than McCarthy the fake news would have roasted that person. The deep state loved his endorsement, they thought they had pulled a fast one on him. By supporting McCarthy they were able to slip a fast one fast them instead. I think it's going to be Jordan and I think that's been the plan the entire time.