Video of Michigan Ice Hockey: Michigan filled the Big House, their 100,000+ stadium for a hockey game. I can only guess a) Michigan Hockey is really popular. b) they marketed the hell out of this all year long. c) tickets where really cheap for this one time gimmick.
Time for "what if"
As successful and well attended as gymnastics is, It's a tough sport to enjoy from even 20 rows up, much less 50. Plus I don't know if you could do either gymnastics or basketball outdoors. I'd say Softball could maybe fill the lower bowl.... vs Tennessee... on a Friday, before Spring Break, market it all year, tons of give-aways etc. I don't think Bama baseball, soccer, volleyball or much else would have a prayer of going over 3,000.