Cheat
It seems the cheat was in looking at the dealer cards with slow motion camera. This goes beyond using mathematics and skill in beating the dealer, and is probably why the ringleader was jailed. I was shocked at first about the 9 months, as I thought they had merely used the technology to crack the maths behind the game by card counting.
Multi-player 3 card poker may well be beaten by card counting, as only one deck is used and strategy is pretty simple (raise on Q,6,4 - but with variations depending on known cards).
The cheat may have been exposed as the casino noticed the players raising on the "wrong" hands and winning because the dealer did not qualify - this would certainly got the attention of the security staff!
They really screwed up by being too greedy, they could have run this scam by staying closer to the strategy, but making subtle variations that could be the result of human error, such as raising on any Queen high when the hidden camera showed the dealer not to qualify.