The "weapons of mass destruction" was kind of used as a pretext because they didn't believe such an argument would win popular support. It's somewhat abstract and rooted in a kind of ideology rather than pragmatism. They also genuinely believed that Saddam did have weapons of mass destructions, but just couldn't prove it. They would be found after invasion. Just a little white lie in the meanwhile.
That's really all there's to it. People get all cynical about "freedom and democracy", but that really was the goal, as a kind of "enlightened self-interest". After 9/11 this only became more acute: with the middle east part of the liberal hegemony, there would be no more Al-Qaeda (or they would be severely weakened).
Because they lied about the pretext, there was little to no broad discussion about any of this so they just operated in their ideological echo chamber. There was no one to really point out this entire notion was perhaps well-intentioned but also rather misguided and ignorant (to say nothing of the execution, which was profoundly misguided and ignorant).
If you prefer to live in the psychological simplicity and safety of "neocons do evil because they're {evil,greedy,powerhungry,...}" or whatever then you're free to do so. But at that point you've also disqualified yourself from serious discussion.
I'm not sure I understand this. If mass murder, propaganda, war crimes, atrocities, torture, money laundering, drug & people trafficking, etc aren't literally evil - just 'normal Western capital' stuff - then what do you call evil?