Why would someone speak highly of a cheater?

I recently Joined a company in the development department and was assigned to 3 married supervisors of whom at least one is cheating with a married female coworker, let’s call her Ashley, he had been working with for about 10 years.

When I was working once with another coworker he went on and on about what a great person and family man this supervisor was and that all of them were like a close family and doing activities together after work with Ashley.

I’ve been there only 2 months and already picked up on the fact that they are having an affair. Why would this coworker who has known and worked with my supervisors not notice it after over 10 years? Or if he knows it, why would he go out of his way to praise him?

Why would someone speak highly of a cheater?
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