For all the bad plays Knox has made this year, the TD catch was one of his best. The throw was way behind him, and he made a great adjustment to make the catch. Sometimes Josh just makes easy throws difficult.
Both the referee and umpire are in the offensive backfield in the NFL so that play where Trubisky was facing away from them made it nearly impossible for the officials to see that foul. When the umpire was on the defensive side of the ball, more of those calls were made.