Kindly consider that I never criticized Iran for establishing a precense in Iraq, all nations flooded into Iraq, Isis itself is a bastard of many fathers, follow the trail and you,l get to the common regional actors.
Iran does have a positive effect on Iraq, if not for Iran, Baghdad would probably be the LGBT capital of the middle east, Isis (and a certain nation backing it
) would have annexed Mosul in the north, the kurds would have encroached even more lands and influence.
Unfortunately, due to its inherent nature, any Iranian influence is bound to increase the polarity in Iraqi society, the Iraqi sunnis view Iran as an existential threat.
Regardless, the Iraqi state was destroyed, it was miserably ruled during Sadam but now there isnt even one, we now have 2 lines of thought acting on the ground, those who are seeking to submit to the US either for material gains or false hopes promised, and those who are against, most of whom aligned themselves with Iran, be it on ideological basis or simply to push a common foe.
As for people cherishing the fall of Sadam, the previous regime was ruthless, illogical, unwise and caused great misery to the Shia population, who were happy to see him go, but the common man is unwise, they could not see what was waiting for them.