Yes, Iraq was definitely not "an accident", and Iraq did not pose an immediate threat to the United States. Rumsfeld and others dishonestly played off of our fear of terrorists/middle eastern states to get support for the war.

That said, there were good reasons to invade. Americans were the ones who put Saddam in power, and no other country was in a position to get rid of him. He was actively seeking to build weapons of mass destruction and had no incentive to comply with the UN inspections apart from the threat of war, and there was a large strategic benefit to controlling some of the oil in the region (this article does a really good job explaining some of the thinking leading up to the invasion; it's summarized in "Caution and Cooperation").

Were those reasons worth the casualties? That's a hard question. When asking that, it should be noted that the vast majority of casualties were due to the civil war. Although the US bears a large amount of responsibility for their failure to stabilize the country following the fall of Saddam, a large majority of the civilian death toll was not directly attributable to US troops.

I am by no means a full supporter of the war. The torture programs were disgusting and unnecessary, the patriot act was a gross violation of the constitution that has both ruined our image and opened the door to authoritarianism, and the attempts to rebuild infrastructure and government were ineffective and wasteful. I just think it's similarly naive to assume the geopolitical agendas of the officials involved were entirely selfish (you didn't directly say it, but you seem to be implying the true reasons for the Iraq war were monetary gain and "dominance").