The title is misleading. There was no loop-hole. There was simply a structure of the game and the people in the article were able to exploit that structure. They were playing the same rules as everyone else. Buy tickets. They just figured out the right time and the right volume for buying tickets.
I don't know how the lottery works, but I imagine he also got a bit lucky. Apparently there wasn't enough people who caught on to the trick to significantly put a dent in his game. He was also lucky that the game wasn't popular enough to prevent triggering the roll-downs. Playing just 7 times a year even over the course of 7 years isn't a great sample size to account for long term variance. I wonder if there was a chance he could have lost money on some plays.