I write about it in an upcoming book. The arbitrary demotion of Pluto puts 2440km Mercury in doubt, too, when the sizes of the “transneptunian objects” are compared to Mercury.
Essentially, a handful of scientists never liked the idea of Pluto being a planet and sought to change it. This was never on the basis of science— the very definition of "planet is pretty nebulous, meaning “wanderer.” When that group of scientists managed to get the change done over the objections of most astronomers and astrophysicists, it cost them dearly: can you imagine how a tenth planet, an eleventh planet, a twelfth planet and a thirteenth planet would have caused a renewed interest in space?
Astronomy and astrophysics survive on grants.
That is now dust, thanks to the ego of a few.