Their entire mindset is based on the presumption of SEC football dominance, which is drummed into them constantly by their program, their opponents, and the TV network they watch. Of course, SEC superiority in the CFP era has nothing whatsoever to do with South Carolina. It's always been them boasting about the achievements of the teams that crush them on an annual basis.
They nourished themselves through all those 5-7 seasons on the ESPN-backed assurance that in any other conference, they'd be 8-4 or 9-3, just a rung below the elite programs (in our case, OSU, PSU, Michigan). Finally(!), a year comes where though they're not invited to the party, they're in the conversation. They get put into a bowl, not with a B1G blue-blood like Michigan, but a program for which they have no regard, or even awareness. They never for a moment anticipated that they could lose this game. Opt-outs? Who cares? Throw 11 guys on the field with SEC patches on their jersey and watch a traditional B1G bottom-dweller melt away. This was their (one?) shot to prove that they were always much more than what their records said they were.
When they realized that we were outplaying them, it wasn't a disappointing end to what was a fine season for their program. It was the harsh realization that all those years when they finished ninth in the SEC, the fact that Alabama or Georgia beat the hell out of Ohio State or whoever didn't make them any better than whoever finished ninth in the B1G. That's what was on the faces of their players. That's what brought Beamer to incoherent rage on the sideline. That's why most of their fans online refuse in any way to deal with what actually occurred between the lines but are obsessed with what, at worst, would be a mild tease using an innocuous officiating signal (though I know it wasn't that).
Everyone loses games, but SC lost the narrative they've been clinging to for decades. That's why their brains have short-circuited.