I cannot speak for O’Mara, but considering that they had to get the first judge removed due to bias, and the second one didn’t seem to be any better, he may have thought he had a better shot with the jury.
The point of an SYG dismissal hearing is to get everything out in the daylight where even a corrupt judge’s actions will be laid bare for all the world to see. No motion made? A crap shoot. ;)