Is it important to be convicted of all your crimes before execution?
Does execution mean ridding the world of a bad guy, or calling someone to account for what they have done? If it is the latter, then they would need to be convicted for that crime first.
In the case of Saddam Hussein, he was responsible for gassing the Kurds, his own countrymen, because he thought the Kurds were going to join Iran's side while Iraq was at war with them. Five thousand people died in that gas attack. Tens of thousands more died in the ensuing drive by Saddam Hussein to dominate the Kurds. So let's just say, they are angry.
And a little disappointed. I guess they wanted to throw a big party, and who can blame them? But don't underestimate the power of having your day in court. It is very strong. People want a feeling of justice and of being heard. And that is exactly what the Kurds did not get with the sneak execution of Saddam Hussein.
Of course the practical reasons for the surprise execution include limiting riots and violence and bloodshed. Understandable. And the upcoming trial of Ali Hassan al Majid, a.k.a. Chemical Ali, will give the Kurds their day in court. But it is not the same as looking your father's killer and confronting him. So anticipate that the Kurds will not be quieted with the mere absence of Saddam Hussein. They were looking for something more: the vindication of being heard.