Why do men cheat so often…so easily?

As a young unmarried man I watched a couple who were friends of mine who seemed perfectly compatible get married and have two children . Money was a bit tight and he was somewhat reckless spending it.. Then in another town before the start of a sailboat race he lost his mind while his pregnant wife was home and he started trolling for women one of whom actually took him up on his offer. In time his Wife found out about it and bingo she divorced him and he never had much of a relationship with his Children after this. It was to my view a perfect example of what never to do. I had many examples of how to behave and how not to behave. I think these examples both positive and negative have helped me be happier in a stable long term marriage where I clearly understand what respect and understanding mean. So far it’s 33 years and we are all over each other every single morning. I am rather surprised that our libidos and physical capacities are as dependable as they are.