Gat's racketeering trial concludes with a summation by the prosecution-- implying that the defense had already summed up their case to the jury. That's backwards. The defense goes last because they are legally entitled to rebut what the prosecution says. A defense attorney can choose not to make a summation, but in the context of this film where there have been public accusations of jury tampering, not making a persuasive-sounding speech at the close of trial could be as evidence of tampering and lead to a retrial.
It seems out of character for a savvy operator like Gat not to be prepared for when he inevitably meets Red, and even after what happens, it seems foolish for him not to defend himself when accused of attacking Red without provocation, and even more foolish to threaten Red's life in front of the warden. Gat's whole "business" model was built on avoiding mayhem, so his sudden brutality rings hollow.
Gats attacked Red because Red tried to kidnap his daughter and threatened to get her when he got out.