How does this even happen?

For context:
This is the base we used for our arena spawn, we had the nurse here and a slime townpet (I believe it was the Cool Slime). Every once in a while both would die and eventually respawn here, but suddenly the Nurse AND the Stylist live here. This is vanilla and we’re about to fight the Moonlord. I’m quite curious on how to replicate this, or at least, know how it happened.