He basically says of himself that he is not an exceptional attorney but a kind of average one, and that it takes him a lot of effort (time) to research and come up to speed in order to be effective in court.  He was an exceptional prosecutor IIRC. I think he's blowing smoke to hide the real reasoning. Maybe his opportunity was to accompany Giuliani to assist in the Ukraine investigation for the big reveal, and that is definitely in progress; if Gowdy joined him in January he would be catching up on a mountain of new evidence and the reveal would already be in progress. It loosely fits with what you say he said. Given that, his next most effective position is at Fox.