(1) People have been taking Trump's word for what the charges will be on the theory that he would know (because defendants usually know)
And Trump doesn't know.
(2) Trump evidently did think that he "persuaded" Bragg not to bring charges. He evidently thought his public attacks and public "defense" and the witness he sent in at the last moment might was enough to deter Bragg.
It wasn't. No surprise.
(3) here is the big one: His political strategy conflicts with his legal one.
8/