Now, this once-existing planet is now a pile of debris – its orbit is an asteroid belt.
What happened to Phaethon was that it was never able to form as a single planet. Jupiter tore it up. The attraction of Jupiter destroyed all the more or less large planetary embryos in the area of the current asteroid belt, and even threw them out of orbit. The total mass of all asteroids between Mars and Jupiter today is 25 times less than the mass of the Moon, what can we say about full-fledged planets.