The 993 date is often put forward as the first example of a canonization performed by a pope (John XV), but it is hardly the first example of papal involvement in the business of sainthood nor did it represent a radical departure from the well-established cult of the saints. Since the ninth century, the papacy had often gifted various relics to churches and institutions throughout Latin Christendom, forging formal and informal ties with the Roman church. 993 may not even be the first example of a formal canonization; some have proposed that the canonization of St. Swidbert in 804 by Pope Leo III may in fact be the first (at the very least he was involved in the process).

It's important to remember that these early canonizations do not represent an immediate, hostile take over of the canonizing process, though over the course of the eleventh and twelfth centuries, the papacy would gradually assert its rights in the canonization process. Initially, however, papal participation was merely a prestigious addition to an already established practice. The cult of the saints had been a firmly entrenched feature of Mediterranean Christianity since the late empire, and by the end of the early medieval period (800-1000) it was common practice for formal canonization to take place under the auspices of local episcopal encouragement and liturgical commemoration. While novel and certainly political, the early examples of papal participation in this process don't represent a drastic break with previous tradition.

I hope that helps. Unfortunately I can't speak much to developments in canonization after the end of the medieval period- the development of the position of devil's advocate is a little beyond my scope.