But if you increase the userbase, you’ll end up with more ppl who like yugioh and want a community which leads to duplicate communities.

Why? That's a pretty big assumption to think a significant share of people will default to create a new community, when the most likely scenario is that they will browse around their own instance to find out what is already here.

Even in the most extreme cases, we have 4-5 "repeated" communities and they all eventually consolidated into one.