Cool stuff Jeremy!
For my 2 cents here...
Everyone LOVES to focus on MIT into events...while that is important its not the be all / end all. I watched the time-lapse video and I can tell exactly what went wrong. Start at 2:20, first 7 seconds it seems manageable...Watch what happens at 2:27 - airplanes start going through localizer, missing instructions, etc...followed by look at 2:35-2:45 arrivals keep pouring into the TRACON from the NW and S. After this point you can start seeing the holds build up, and probably happening at the center level also.
My point is nobody says anything until its to late, it usually goes "Hey im swamped hold the traffic!" but after you watch this video you can clearly see this coming. I am sure you had a dedicated TMU person, but usually because of staffing they are either working something, or trying to look at big picture. This becomes very easy to miss the small stuff, in this case the TRACON situation.
For your next event I would (if you can) have a few people working TMU, one for Center, another for TRACON. Utilizing ground stops and MIT won't fix bad pilots, or go arounds, or any of the other daily issues we all face when working event traffic. They certainly help but don't overlook what is happening or what is about to happen in the TRACON. From my experience even the best controllers won't say anything to TMU until its to late.