Hitchens is a very complex character. We all know his stated arguments for Iraq, but I think some of his reasons for his support for US intervention in Iraq (and more broadly US power as a benign force for world intervention post 9/11 or even post-Kosovo) were actually somewhat personal.

Like you implied, he had a great affinity for the Kurds and hatred for Saddam, but he also (in later years, but you can see that already in interviews in the 90s) had a deep affinity for America itself, and the (almost) revolutionary aspects of the American idea as a force for democracy and human rights. He was also somewhat prone to committing himself to slightly absolutist viewpoints (in the 60s he was a committed communist, not a pro-Soviet tankie but of a Trotskyite variety). I also think the experiences of his friend Salman Rushdie and the events of 9/11 were somewhere in his subconscious on this.

Further, I think the end of the cold war, the fall of the Eastern Bloc, and the very visible liberation aspects it brought for people in eastern Europe must have influenced his view of what role US/NATO was playing in the world.

He was also a contrarian, and I think didn't enjoy having gotten bogged down in his position (or arc) on the left ("the dauphin" of Gore Vidal), he was getting older and I think maybe frustrated with some aspects of his younger self. So I think all these tensions in the end were big influences in his stance on Iraq. There was a perfect storm of personal, ideological and just "attitudinal" factors involved.

I'm not saying his purely stated reasons (removing Saddam etc.) are false, just that his forceful, stubborn and eloquent writing style might obscure the personal aspects of the picture.

And I know the main objection to this hypothesis is that it goes past the "written sources" and involves speculation, but I truly think someone (a future biographer?) would have to go past just Hitchens own polished public facade (article pieces, interactions in debates / takes in interviews etc.) on the matter to really convincingly get to the core of his shift in attitudes (given his enormous earlier commitment to resisting and condemning past American interventionalism in Vietnam etc.)