Why the heck was there an Agapetus I?
Pope St. Agapitus I (d. 536) took the name of a Deacon Saint Agapitus who was martyred with Pope St. Sixtus II in 258. Deacons in the major cities played very important roles--when the church in a given city was small enough to be administered directly by a single bishop, the deacons were their right-hand assistants. Priests were not yet important, though there were elders (presybters) who served as advisors to the bishops but who did not yet have all the sacramental functions, especially the Eucharist, delegated them--the bishop could handle the sacraments himself, for the most part.
As high-profile Christian leaders, these early deacons were targets in persecution--Lawrence of Rome, Vincent of Saragossa in Spain etc. So their deaths were long remembered in the churches they served. The persecution of 258 was one of the worst (empire-wide persecution only began in the 250s), though dwarfed by the last one in the 290s and early 300s, and because it was so violent it was long remembered.
Agapitus I tried mightly to heal the rifts between the Greek and Latin churches--his name itself is Greek, reflecting the time (250s, Deacon Agapitus) when most Christians at Rome were of Greek background--until about 220 the liturgy was celebrated in Greek at Rome, not in Latin. The earliest center of Latin Christianity was in North Africa, not Rome--but that changed in later 200s and the 300s.