I actually used to be more into cuckoldry and fell out of it. I'm more into sharing now. The key to understanding it, at least from an intellectual perspective and not emotional one, is that it all comes from a place of pain. Turning pain into pleasure, aka masochism. That is all to say that it probably holds more for people with self-esteem issues, lack of sexual confidence, past trauma, and/or various other forms of inner turmoil. If you don't feel that, then that's likely a good thing.
The cuckold fetish is a lot of things. Not everyone with it has self esteem issues. I would argue if you have a self-esteem problem, then cuckolding might be unhealthy as you might progressively try to constantly relive personal trauma.
It's important to differentiate cuckolds as portrayed in porn and cuckolds who exist in real life. Ultimately there are perfectly well-endowed men with good careers, personalities and well balanced romantic lives who STILL have this fetish and some actively practice it with their partners. There are also so called "alphas" who actually have deep insecurities hence they engage in performative displays of dominance or "confidence" in an attempt show everyone else they're better by degrading or leveling themselves above others to "prove" something they should already know and understand from a deep seated and true sense of confidence.
Anyway there's a million ways to practice cuckolding and not everyone fits so neatly into psychological and status oriented boxes like alpha male vs beta male etc.
If you grew up with your earliest sexual experiences being porn for example, a cuckolding fetish can develop because you're most comfortable and turned on seeing a woman get fucked from different angles and being able to focus on her pleasure and experiences in ways you can't when you are the one fucking her. You get conditioned into it, and gradually lose interest if you stop watching porn and gradually "train" yourself to get aroused from other more direct means.
If you spend most of your life trying to meet certain standards and perform (whether you're a high achiever or you always lead and make decisions) then there's a lot of relief and relaxation in being degraded or forced to feel rock bottom because now you have no standard to meet, no task to perform and you are being led rather than leading. You're now in the back seat and your wife/partner is doing the driving with another man. Humiliation can play a big role in this but more to do with being relived of responsibility and emotional labor. Imagine for example how it feels if you're on a road trip and halfway through after 10 hours of driving someone else offers to drive and you get to sit back and enjoy the scenery? It's like that.
Finally while I'm sure there's masochistic men who want to be humiliated because the angst feels good but its not the only reason. Sometimes men find their partner more desirable if they see her fucking other people. She becomes hotter, it triggers some primal urges like sperm competition. I also think cuckolding wouldn't nearly be as popular as it is if the taboo around extramarital sex was less pronounced or if women were shamed less for having high sex drives or wanting to have sex with multiple partners. Some people just get off on the idea of their seemingly proper wife turning into a massive slut doing what is normally forbidden or what she "isn't supposed to do".
Long story short cuckolding has a lot of angles, many of them don't have anything to do with your self esteem or your manliness. In some cases getting your partner to cuckold you at your behest is a sign you're incredibly confident in your worth as a partner to them that you think they will still return to you despite having intimate sex with another man whereas someone more insecure would get angry or violent.
This is just my opinion but I think a lot of men go into relationships with a scarcity mindset "I gotta lock this one down because she's so amazing and I can't do better" vs "I really like this person and I can see myself spending my life with her. But as much as it would hurt for our relationship to fail, it's not the end of the world, I will meet someone else who's better suited for me and I am comfortable enough with myself as a man that I can be alone until that happens again".
Many people will repeat the latter sentence as a mantra while harboring deep insecurities and not truly knowing and understanding that they're still valuable. Whether you have value as a partner or not is a choice you get to make and people will automatically fall into your headspace with you if you cultivate genuine beliefs and faith in yourself. Unfortunately it does take faith, you have to unconditionally love yourself the way a parent loves a child or a dog regardless of how badly they fuck up. When you can create that sensation within yourself you don't need another person to make you whole and suddenly the risk of losing your partner to another man does not become as life crushing as it used to be (unless you're married and they take half your wealth).
Long story short, confidence issues masquerade in a variety of coping mechanisms that range from wanting to be cuckolded to reinforce self limiting beliefs to performative behaviors where you constantly degrade others, or try to hit on their girlfriends to prove something. Gotta look past the ACT and look into the underlying reasons WHY you are doing the act.