Well Ruud who runs .world also runs Mastodon.world which is a fairly large mastodon instance, so he is somewhat of a known quantity and has experience running large Fediverse servers. His mastodon server has handled a large population and donations happen through Open Collective for transparency as well. He also runs Calckey.world though that is much smaller.
Not really. Also by your logic you can’t trust anyone ever because there is always a risk they turn bad at some point in the future. All we can do is evaluate what we have in front of us at the moment. Current evidence suggests Ruud is trustworthy, committed and capable of running a large Fediverse instance.