Because, of course they will convict. No evidence. Faked. What are they going to do, admit it? No they will convict. Presumably once they do, the illusion will be fully shattered for most reasonable people. Then... then with a bit of luck we get the footage of the fake attack being planned, Babbit makes an appearance or whatever. (I saw a video from pre-noon of them staging the "glocks at the chamber door" photo - surely there is comprehensive CCTV of the whole thing).