Come to think of it, though, what is the sensible way to use some vast number of credit card numbers to enrich yourself? I assume small-time credit card thieves can get away with it because they're sufficiently small-time to escape an in-depth investigation, but is there any way to untraceably pay yourself?
Selling them. At 5$ a piece they will make 375 million dollars. People who buy them are then most likely to use them for this kind of purchase, where it might be hard to get caught.
I'd bet that it's not the person who stole the 75e6 credit cards that is buying gas, someone bought that number for $5 on some shady site.
You're assuming that the police care enough to actually investigate the crime. From my experience in web-based sales, the authorities don't seem terribly interested in pursuing cases of credit card fraud.
(If this weren't HN, I'd add something sarcastic about them being too busy hunting down speeders and feeling up travelers)
Certainly possible that it's purely coincidental, but seems unlikely.