Nah, Tullius is by far the biggest idiot in the whole Civil War.
Ulfric surrenders, which on its own seems stupid but when you realize he wanted to be put on trial to make a statement/scene, it at least makes a little bit more sense.
What doesn't make sense is Tullius going along with it and not executing him right there at Darkwater Crossing. Instead he seemingly starts taking him to Cyrodil for a trial. Only to, for some reason, turn around and head back at the border.
So either Tullius realized this was a fucking stupid idea and was playing into whatever plans/ideas Ulfric had, or he was ordered not to bring him to Cyrodil for a trial. Either way, instead of just executing him right there...he decides to take him to a backwater fort town to put on a show execution for a group of a dozen or so peasants.
So then he gets to Helgen, and instead of executing Ulfric right away he executes some random mook because he asks them to? And then instead of executing Ulfric right after him, he lets some dipshit Captain order some random stranger they picked up to be executed because she seemingly had a grudge against them.
He had Ulfric for TWO DAYS, and didn't finish him off. Are Empire/Tullius fanboys just retarded or not paying attention?