She ran a stop sign and she didn't signal.
So, why didn't the out-of-jurisdiction state trooper tell her about running a stop sign when she asked? Why did he only tell her about the failure to signal a lane change?
I submit that he would have had to write her a ticket for the stop sign, but could just give her a warning for the lane change, so that's what he did.
He was killing time on a college campus, is what it looks like to me. I suspect it looks like that to his bosses, too - which is probably why he's been suspended.