Sometimes the evolution of slang really gets out of control, because originally a cuckhold was defined as the man who knows his wife is cheating on him and does nothing to stop it; there had to be that element of cheating, meaning he didn't want it, which is different from a guy who is perfectly okay with a wife that fucks around.
"Cucking" is a nebulous term, which only becomes somewhat clear in random context -- but no matter how the concept is specifically being explained, it's got nothing to do with the actual manifestation and everything with trying to emasculate someone. It's about that powerlessness, or more precisely: it is trying to make someone feel powerless with the concept of cucking. Back in the 80s it was calling dudes gay. Then retards. It's all the same: sub-level bullying ("bullying" itself being another weaponized terminology of coercion; ditto "weaponized").