Tipton’s extra lines of code first checked to see if the coming lottery drawing fulfilled Tipton’s narrow circumstances. It had to be on a Wednesday or a Saturday evening, and one of three dates in a nonleap year: the 147th day of the year (May 27), the 327th day (Nov. 23) or the 363rd day (Dec. 29). Investigators noticed those dates generally fell around holidays — Memorial Day, Thanksgiving and Christmas — when Tipton was often on vacation. If those criteria were satisfied, the random-number generator was diverted to a different track. Instead, the algorithm would use a predetermined seed number that restricted the pool of potential winning numbers to a much smaller, predictable set of numbers.
Admittedly, this is based only on the description from the article, which says it is describing pseudocode. But obviously, once this code is found, it's game over. Apparently the audit process for lotteries is terrible enough that this didn't matter.
Compare this with the auto emissions cheating scandal, where the algorithm was complicated in order to hide what was happening, so that the code would not be obvious as a defeat device: http://cseweb.ucsd.edu/~klevchen/diesel-sp17.pdf (see pages 6-8).