Your argument makes sense but there is a reason why the rules are there for a reason, he has a conflict of interest and in many occupations the way it deals with this is the same, you need to choose one or the other occupation and never both, a lawyer cannot at any moment take two different sides of the same case, he can only hear one side and the moment he does and receives payment he cannot even listen to the other side or he will have an unfair advantage and the same is happening here.
I can understand the argument put forward by UEFA. Being a player, Zlatan should keep away from gambling sites. If he has an interest in the gambling sites, then it gets murky. The amount of profit his company is going to earn may change as per the outcome of the matches in which he is taking part. But my question is not related to the fairness of the charges against Zlatan. My question is why the UEFA dragged on their investigation, despite these facts being known for so long. The news first came to surface in 2018. Why they were in deep slumber for all these years?
That is impossible to know, but there are some possible reasons for this, one possible explanation is that as we know legal processes have the tendency to move at a snail pace compared to the world in which we live in, another factor could be politics, maybe there were some higher ups that liked Ibrahimovic and they moved their influences to protect him and to delay this, and finally maybe they are that incompetent, something that is not really difficult to believe.