> literally a trading card company that found themselves operating as a bank.

Karpeles did not buy a trading carding company or even a former one. McCaleb did have a temporary Magic-related site at mtgox.com 4 years before he started the exchange, but literally the only thing the two shared in common was the domain name. I recently finished researching & clarifying the early history, if you are interested in the details: https://en.wikipedia.org/wiki/Mt._Gox#History