You can read the PNAC letter that laid it all out.
http://www.militarist-monitor.org/images/uploads/PNAC_Letter_to_President_Clinton_on_Iraq.pdf
the safety of American troops in the region, of our friends and allies like Israel and the moderate Arab states, and a significant portion of the world’s supply of oil will all be put at hazard.
The reasons were freedom of attack from American military installations, Israel, US-aligned monarchies in SW Asia and oil.
GW Bush, Joe Biden, and Hillary Clinton were fully aligned on this and helped the invasion happen.
Biden was there Chairman of the Senate Foreign Relations Committee in 2002-2003 and ensured that only pro-invasion witnesses were welcome.
It was a bipartisan exercise in American power to secure further American power and they fully intended to continue the slaughter into Iran.
None of this is a mystery, and fuck that "teacher" for lying about that.
Additionally, this was a time when a number of bloggers were being invited into Serious outlets like the NYT and Washington Post. The #1 qualification to get such an invitation was to have been in favor of slaughtering Iraqis. E.g. being wrong about Iraq was effectively a job requirement. That was the crop including Matt Yglesias, Ezra Klein, and Megan McArdle.