The pundits and those on the left got and continue to get this wrong. We didn't invade Iraq in order to get the oil for Haliburton or complete the job that should've been done in Persian Gulf War I. We invaded and easily conquered Iraq for reasons which these folks "seemingly miss", which I don't believe is because they're obtuse! There were three potential countries in the Middle East which we could use to provide forward basing for the continued war on terror: Iran, Iraq, and Syria. Syria probably would've been easier than Iraq and while Iran probably would've been tougher--it is/was unlike Iraq, probably more amenable to "nation-building." But in neither country did we have
causus belli. That made Iraq unique.
One would have to be a poor student of geography to not notice Iraq's location with regards to those other two countries. We know that our invasion has had an effect on Syria, plus the others mentioned in the article and maybe if we're lucky it might forment a popular uprising in Iran and result in the overthrow of the mullahs. Not too bad for killing not two birds, but a few birds with one stone