(although if we're speculating with perfect hindsight then he would have probably been toppled during the Arab Spring anyway but who knows how that would have turned out)
Assad is still holding on in Syria, so I don't see why Saddam would have "probably" been toppled in the Arab Spring, in the event of no US intervention.
(Though that is a question, how likely is it that there would be no US intervention, years after 2003, by Bush or some other president? Were we going to enforce the no-fly zones forever, and not really push it much farther than that if there had been some attempted uprising in the 2000s or 2010s?)
