Its very natural for fediverse projects to have a few of the starting instances dominate, at least at the beginning. Its not necessarily that hosting requirements are heavy, its just that beta software under rapid development needs frequent updates.
This is the instance run by us devs, and we can't do more than encourage people to start their own instances, and for others to federate with them. There are no ads on lemmy, so we don't gain anything by having more users. More traffic on this instance is actually detrimental to us, because it gives us more moderation work, whereas we'd prefer to do development.