I wasn't involved in the production.
However, prior to my recent retirement, I spent the final decade and a half of my career at the RCA Dome, and subsequently Lucas Oil Stadium. I was involved in the very first technical, logistical discussions and meetings regarding the Superbowl, and the halftime show from day one. I'm certainly not uniquely
qualified, however I'm entirely familiar with the technical complexity of the production. It was superb,... visually stunning. Additionally, when listened to at home, the audio quality was good over my reference system. No, the bass wasn't muddy as a previous contributor stated.
Regarding tracking, or lip syncing; the landscape changed in the 80's and 90's whereby acts like Madonna, Janet Jackson, etc, pushed the stage show into a realm whereby elaborate costumes and perfectly timed special effects, blended with heavily athletic moves/dancing, and combining all these elements into the larger scope of the production pushed the actual singing off the top spot,.. with regard to order of importance. The larger multiple-component visual element, became of paramount importance.
Obviously, a nice side benefit to tracking the vocals is added headroom/dynamics, and freedom from any issues from feedback. If I recall correctly, there was an open mic and some feedback occurred early in the performance. In an acoustic environment such as a stadium in the round, the acoustic summation that occurs in the middle of the venue can be a nightmare scenario. There are tools to mitigate such things, however problems do come up. Choosing to track the vocals isn't viewed as any less a performance in my opinion, actually it's clearly the prudent thing to do. The vocal quality of the small head-worn mics is highly compromised over that of a full size diaphragm mic. Although I've never mixed any production when lip syncing is used, I am somewhat familiar. Typically, when lip syncing is done, the vast majority is tracked, then one may bring up the mic for the conclusion, thank yous etc. In this case, Madonna dropped down into the staging, a touch too soon as she could be seen plunging. I'm not certain, but if I were to guess, I'd think the intent was to wait a moment longer to make it appear as if she disappeared entirely.
The Gladiators, etc, were locals,.. firefighters, fitness buffs, dancers etc, recruited for their roles. The drum corps were also local high schoolers. The Drum Corps International, (DCI)
world headquarters is located in Indianapolis, so stellar drummers are in strong supply. Anyway, knowing the electrical, electronic, logistical, and physical issues involved in pulling a show like that off, it's phenomenal.
A mere 8 minutes to set up, 12 minutes to perform, and only seven minutes to tear it down. And if you've not aware, rolling anything remotely heavy across field turf full of rubber chunks is a real bitch. Sure elements were less than perfect, however I thought it was great, very creative, and seemed to flow relatively smoothly. Also, when it's examined in the entire context of the logistics encountered, it was superbly done in my opinion, and in my experience.
My 2 cents