Not OP, but if I had to guess, the coder just looked for the most favorable 'prop bets' that books use to get the casuals in the door and took advantage of those favorable odds.

Not really any other way to do it without fixing games.

They were probably taking advantage of the rush of companies into the US market. It's a common market penetration tactic to offer odds that are wildly favorable to the punters for the first few months.