I am thinking that the reason he is filing a criminal suit against seven people is based on what his lawyer has recommended. If he files a criminal complaint against people with insufficient evidence, it makes it more likely that the whole matter will be dismissed quickly. So they probably pared it down to the ones they felt they could make a case against, as thin as it might be. They don't need for it to succeed, they need to file it for the next step.
Because it could be that this is just part of the process for filing the civil action. If he files the civil action after letting the statute of limitations on the criminal complaint expire, it could hurt his case. Since defamation is treated like a crime, there would be the question of why he didn't file charges if he felt that a crime had been committed. So his lawyer may have advised him to pursue the criminal case, knowing that it will go nowhere but that it is a necessary first step.
Mind you, the civil case has no real chance of succeeding, IMO. Even if, by some odd circumstance, he was able to get a judgment against anyone, he would be in no position to collect it. I doubt that Croatian courts can attach a lien to any funds/property that are not, at the least, held in Croatian banks or on Croatian soil. He would be able to wave the judgment around and pretend it vindicates him, but that gives his critics yet another chance to mock him. I don't think he understands the long-term consequences of his actions here. But self-preservation seems to take second-stage to his pleasure-seeking.