Sure, it might have been interesting to study Saddam’s psychology. But that was not the point at all. Saddam needed to die. He needed to die because he had done some atrocious things and death was the only just punishment that could be imposed upon him. He needed to die to put to rest, forever, the possibility that he might somehow regain power in Iraq.
The manner of Saddam’s execution was brutal by U.S. standards, and the Iraqi executioners were, shall we say, less than professional. Still, hanging is a relatively quick death, and it came after a trial with the indicia of due process, which is a great deal more than most of Saddam’s victims got. Saddam even got to get a last political swipe in — his last words were to mock Muqtada al-Sadr for being little better than a small-time thug, which compared to Saddam, is exactly what al-Sadr is.
The prospect of keeping a man alive only to be studied, like some kind of lab specimen, seems itself to be dehumanizing and cruel. It’s entirely possible that Saddam, who was quite an intelligent, crafty fellow, would have made a game out of warping the data.