Iraq, not Iran, but yes definitely to "finishing what daddy started." In 2002-2003 the W's cabinet was chock full of people who got their leashes yanked on the Kuwait/Iraq border because Daddy Bush respected international laws and norms. They were steam rolling toward Baghdad basically unimpeded. They could taste that sweet sweet oil and a major military victory over an aggressor state that would send a strong message about the sovereignty of international borders.

It sure as shit scared the hell out of Saddam, too. Probably that's why he got all paranoid.

With hindsight and if we assume that the US was going to invade Iraq either way (in 1991 or 2003), it would've been better probably to just do it the early 90s, before the was a robust international terror network to step into the void.

Overall, I think it was justified to invade Afghanistan immediately after 9/11 and depose their government, but stop there. I don't know what the best "after" would've been. Definitely not putting all our focus into Iraq. Perhaps with all our resources and world focus on actually rebuilding Afghanistan instead of pivoting to Iraq, we could've helped them succeed instead of running from place to place putting out fires while it smoldered.

So no way was he going to pay for his crimes.

What specific crimes?

I think his and his administration did a lot of awful shit, but they did it using politics, not by breaking the law. They painted their opponents as un-American. They whipped up fervor saying that "you're with us or you're with the terrists" and changed the "French Fries" in the congressional cafeteria to "Freedom Fries" after the French refused to jump on board with their war plans. They made sure the public was scared, because scared people are easier to manipulate. But, fundamentally his administration did it so that they could win votes in and for the house and senate. Fundamentally he still followed American law.

There are various things where the administration or the military might have violated international laws against war crimes or aggression. For example, the treatment of the prisoners at Abu Graib, the whole existence of and infinite detention at Guantanamo Bay, and possibly even the invasion of Iraq itself. But, international courts require a much higher burden of proof, especially to pin the crimes on the head of state. And, Bush had pet lawyers like John Yoo producing memos to declare it all legal.

Evil shit, especially evil done by the military in other countries is almost never going to result in criminal charges, let alone convictions. Trump is unusual in that the crimes were so incredibly blatant. The normal method for most shady heads of state is to at least go for plausibly legal. They have access to tons of lawyers willing to bend over backwards to declare what their bosses want to do as being legal.

People need to stop equating "evil shit" with "crimes". Yes, Bush and his administration was responsible for a lot of evil shit. He was responsible for hundreds of thousands of Iraqi deaths, thousands of deaths of soldiers in the bullshit "Coalition of the Willing". He was responsible for indefinite detention without trial at Guantanamo Bay and torture at Abu Graib. But, with all that blood on his hands, he may have done it all without breaking any laws. There's a reason why the prisoners are being held in Guantanamo Bay and not on US soil. There's a reason that the torture happened in an Iraqi prison. A big part of that is that many US laws don't apply to those places, so while it's awful, it may not be illegal.

Sometimes I wonder if the DRA would've succeeded if the CIA and MI6 hadn't been backing the Mujahideen.

https://en.m.wikipedia.org/wiki/Operation_Cyclone