What did the instances of cheating among Sumo wrestiers and the teachers in Chicago have in common?

The connection isn't between the instances themselves but instead the underlying notion of how with the right incentives a person would do anything. The incentive of win or be bumped in sumo wrestling is enough for the wrestlers to cheat. For teachers it's a multitude of things, e.g. the money, keeping their jobs. Things like that is the connection rather than the straight fact that they both cheat.