The Iraqi insurgent demands were for the US to promptly leave (not occupy the nation for over a decade) and they were also happy to have Saddam Hussein's regime

The Iraqi insurgent demands were for the US to promptly leave (not occupy the nation for over a decade) and they were also happy to have Saddam Hussein's regime gone. The mass population of Iraq was very clearly not against the US removing the regime either. The primary disastrous mistake the US made was the very poorly planned occupation and dismantling of most of the existing government structures (amplifying the chaos and civil war risks).