There was a lot of misinformation at the time on Iraq's military capacity. I know, because I was busy buying it hook, line and sinker.
Quick confession: I was a flag-waving redneck conservative at the time (and all of about 14 or 15). I was one of those people who actually thought protesters should be shot for treason.
Anyways...while they may have had a significant inventory and a large conscription base, their ability to actually mobilize and field that army was sorely overstated. And the big thing was that it was a potent army *for that region*. But going up against a 1st-rate military, their airforce and air defenses were outclassed (and most of it destroyed on the ground). Once the Americans were allowed to establish air superiority, that large army began just so many ground targets.
It's kind of sad, in a way. The Iraqis weren't as potent as we were all warned at the outset of the war, but then because they collapsed so quickly, the public interpretation was "Wow, they really weren't very tough at all," which is also inaccurate and which deprives the US military planners of the credit due them. It was a perfect storm as far as military operations -- poor Iraqi morale and battle doctrine, excellent Allied planning, and an early acquisition of air superiority which allowed overwhelming firepower to be directed onto Iraqi ground formations with little to no capability for them to return fire. After suffering withering and continuous aerial bombardment and missile strikes for weeks, it shouldn't have been that much surprise in retrospect that entire formations were surrendering to the first foreigners they saw.