Poly hyas significantly lower rates of cheating (although that can still take place) because the relationship style allows for multiple intimate connections done openly and honestly. Polyamory also demands good communication, being responsible for your own emotions and other things that would make any relationship function better.
People are still human, and most of us have to do significant work to deprogram from the bad habits we picked up in most monogamous relationships where people tend to overly rely on the "rules" rather than what the parties actually want, but over all, since nothing is inherently "wrong" if it has been agreed to by both/all parties, there's a lot more room for individual needs and wants to be expressed without feeling like you are doing things incorrectly. With no inherent relationship rules, the parties involved have to co-create the relationship themselves, and no two poly relationships are exactly the same. Then they have to keep communicating and working what they have designed to keep it healthy. Naturally, not everyone is going to be self-responsible or mature enough to do this, but it's still a lot higher percentage than those who are relying on a relationship style and it's parameters that were designed by other people thousands of years ago.
The divorce and cheating stats are relevant because a lot of that takes place due to the rules and constraints of monogamy, which do not inherently exist in poly. Plus, as the graphic from Esthel Perel says, the things that tend to bring stability also can stifle desire (particularly for women).
Monogamous people often cheat because the relationship is stale, the sex is bad, or they are otherwise not getting something that they need. Poly people can maintain the relationship(s) they have and get anything else they want or need from someone else without having to break the other relationships. Poly people who cheat are those who either enjoy having a secret or they are unwilling to do the hard work that clear and on-going communication requires. It's pretty different.
