On the other hand he is addicted to being unfaithful.
Neymar is a typical example of person who lives for the world. He 'masters' the material world, having access to all the facilities, pleasures and comfort disponible for wealthy and influent individuals. For that reason, I think your phrase above is totally accurate and summarizes the description of Neymar very well, because when the person focus only on material stuff, he will be easily dragged by addictions and ephemeral pleasures, which don't mean anything on long run, while giving up on his human essence, which involve deep feelings of peace, self-consciouness, welfare which demand sensibility from the individual to be experienced.
If the person loses contact with this part of his existence, inevitably he will become unfaithful, empty, cold and indifferent to people and moments which should be important and full of meaning for him. I guess people start living on an automatic mode, shutting off their conscience more and more each new day and each new bad choice they make for their lives, worsening symptoms of addictive behavior, and even worse: symptoms of unfaithfulness...
I think every human being wants to live a better life in the world so many people strive to reach a higher level of life, myself included.
It's very easy for you to judge people in this context, for me personally this rather than explaining at the level of impact of the Human itself when the position is the same as Neymar is very subjective and human relativism will cause different outputs on what they have done with gambling, whether it's abnormalities or unfaithfulness that may occur as you said, but for me personally this also depends on the response of his environment and also his family regarding the character that is in neymar, maybe you can say it in such a way, such as the popularity of wealth and getting access to all the luxurious facilities and finally plunging into addictions that will cause the bad nature of man to come out, we cannot be sure with just the naked eye in analyzing this kind of thing, but whatever it is called a very bad addiction will turn someone into a bad human being, such as drugs, women and including gambling, if the addiction suffered is in the final stage.
But we need to remember that maybe because Neymar today has many facilities to access all things easily, he is not worried about himself and the future of his family.