Some Olymen, known as Oracula, bonded to Olympus dragons to read prophecies. Once, one read a prophecy that if the Divine Dragons stayed at Mount Oly, the whole Olymen race would be destroyed. Thus, the Olymen banned the Divine Dragons and their Odes.
Recent study turned this out to be untrue. Those Oracula clearly weren't good at reading prophecies, since the prophecy read the opposite: if the Divine Dragons LEFT, the Olymen would become extinct. It is unknown why, but the last traces of the Olymen date from shortly after the Destruction of Divinity.