The wealthy class is who is usually first to turn on the sanctioned government, not the poor. The wealthy are who change things, and they will always change things to suit themselves. Maybe the poor riot, hopefully they don't starve - international humanitarian aide (e.g. dropping bags of rice) is pretty savvy these days... Plus there is always the assertion that a sanctioned government whose people are suffering is a government that requires change - the whole point of sanctions.
Sanctions make change more suitable for the decision-makers (Oligarchy) than doing nothing. Sanctions work or they would not be used. Of course the poor suffer first and most, that's always the case in peace or war, right or wrong.
I would speculate that the oligarchy (Sunnis) of Saddam's era were not 'sanctioned' enough to confront him during those 13 years.
(It was incorrect for the USA to leave Iraq during the first invasion 20 years ago at the UN's behest. The Bush family had to regain the Presidency to right that wrong. They had death threats from the Shiites that were abandoned in the South of Iraq because WE left them to Saddam. Aweful 13 years of suffering and murdering. I don't wonder why Bush Jr. lied in order to attack Saddam, its obvious to me. Back to topic...)
Know that I have not been to Iraq and cannot speak from first hand experience.
Art of War states that removing an enemies capability to wage war is plan #1, and %100 more effective than the always ill-fated occupation of enemy territory. It's just about the first thing stated in the book; (we call it passive aggression these days).
Did you go to Iraq during the invasions?
No,I didn't go to Iraq. I was still a civilian in 1990 and was already on permanent leave the second time around (and since my squadron was eventually deployed elsewhere, that wouldn't have happened anyway); which means I don't have any first hand experience on the matter either.
I'm just basing my observations on history and documentation which, as I mentioned, don't support sanctions as being effective. I believe the reason why they are used is just that they are as far as the UN can manage to go. And since their effect is only captured in abstract statistics, they are considered morally more acceptable. Numbers are always elusive and controversial, but are still unsettling, regardless of which ones you believe and how you apportion blame.
As for the rest, I'll have to reread the Art of War, but I believe our disagreement is due to the fact that you seem to consider invasion and occupation like interchangeable terms, while I don't.
I'll leave it at that before I drag this further out of topic.