I can't read the Nature Astronomy article A kilometre-sized Kuiper belt object discovered by stellar occultation using amateur telescopes because the library I use doesn't subscribe electronically.
However I can see the bibliography and the word serendipitous appears the titles of two different references, and that makes me think that the observation described in the paper was in fact serendipitous.
Question: On average, roughly, how many amateur telescopes are looking for serendipity in a coordinated fashion? A few? A dozen? How many "professional" telescopes or those funded for science are involved in this campaign as well?
One example of an organized campaign looking for serendipity is in Japan, which is described in The Universe Today's Tiny Object Found at the Edge of the Solar System for the First Time. A Kuiper Belt Object that’s Only 2.6 km Across.