Complex sentence: During the early to mid 1970s he gained widespread notoriety for perfecting techniques to do team card counting in numerous casinos worldwide, earning millions of dollars from the casinos, with some bets as high as $12,000 on a single card.
Split into simpler sentences: During the early to mid 1970s he gained widespread notoriety for perfecting techniques to do team card counting in numerous casinos worldwide. He earned millions of dollars from the casinos, with some bets as high as $12,000 on a single card.