Actually, they had approximately 3 million people, and only 800 porta potties (government planning at its best!). Here is a video of a fight that broke out after one of the potties collapsed and poured feces all over the ground.
https://truepundit.com/one-video-perfectly-captured-eagles-parade-porta-potties-explode-fans-brawl-fecal-waste/
Bud Light was also providing free beer to everyone, due to a bet they had made before the season. Overload an area with some of the most hard core football fans, then provide free beer and inadequate bathroom facilities. What's the worst that can happen?