Occasionally, market professionals make mistakes, and the bullish unusual options volume for CarGurus (NASDAQ:CARG) seemingly appears to be one of them -- at first. However, such optimism for CARG stock may confuse investors because last year, the Federal Reserve raised the benchmark interest rate multiple times to combat skyrocketing inflation. So, investors simply need to do the easy arithmetic: aging vehicles plus a heightened need to spend as low as possible equals a surprisingly bullish case for CARG stock.