It follows the first to market principal in many of the most active communities, and it is the most federated instance. Many instances that are not federated with each other are federated with .ml. You still won’t see those comments between instances. Like from my main account here on .world, I can’t see hexibear or beehaw stuff, but from my .ml account I can see them. I have accounts on many instances in order to help federate new communities and to check biases/instance behaviors.
I came over a few days before the rexodus and subscribed to the active communities before the influx. That sub list is still centered around the most active communities, and the majority of those are from .ml and before I joined Lemmy.
Instances all have different flavors. I don’t like using my .ml account as a main. I’ve tried it. But I find they are the center of the most interesting and productive conversations for a more broad audience, while Beehaw has the most positive and friendly conversations overall. The main benefit to .world is the speed of connectivity, general audience scope, but with a strong anti asshat policy.