Thing is, NO sane informed theory involves Pluto springing into existence and achieving a tranquil orbit in just 100 human lifespans.
Pluto was discovered 85 years ago and has on a 248-year orbit. It has not even been known to humankind for half a trip around the Sun yet. Calling the orbit “tranquil” is highly speculative - its planetary system sure isn’t tranquil by any stretch of the imagination, it is highly chaotic. We don’t even know for sure whether it is capable of completing one single, full stable orbit; the observational data isn’t there. Heck, we didn’t even know how many moons it had until New Horizons got close to it.