GameStop (NYSE: GME) posted a striking divergence in its most recent quarter, with operating income surging to $160.2 million from just $66.4 million a year earlier, even as total revenue declined 18.7%. The driver behind that profitability leap is a business most investors once overlooked: collectibles, which generated $356.3 million in revenue during the second quarter, a 56.5% year-over-year increase. That single category now accounts for rou…