I believe that a lot of POTUS Trump's tweets are designed to keep pressure on Horowitz and prevent a whitewash.
I also believe that Sen. Lindsey Graham is sending a message to Horowitz. The Senate already has the information...don't attempt a whitewash.
I don't know why Sen. Graham changed, but I sure like the new Sen. Graham much better than the old Sen. Graham.
Just my humble opinion.
I feel the same way about Graham. His switch surprised me. And Jeff Session had me fooled. I liked him, thought of him as one of the few politicians I could trust, and then he turned out to be a Deep State plant used in case somebody such as Trump might win.