NATO is a treaty pledging all members to come to the aid of a member who is attacked. It is a mutual defence treaty. So when you say “WHAT?!” I assume that indicates you are ignorant of the basis of the NATO treaty.
NATO didn’t attack Iraq, the USA did, pulling in a “Coalition of the willing”, initially Great Britain, Australia, Poland and the United States. That’s not NATO, although some other NATO members joined later. I don’t think the invasion of Iraq was justified either, but don’t confuse the Coalition with NATO.