There have been men throughout church history who have tried taking control of the Papacy by overthrowing the elected popes. These people are known as antipopes. Motivating factors for such actions have been varied, in the words of one encyclopedia:
"...Historically this situation has occurred as the result of various causes, not all of which imply bad faith. Antipopes have risen by violent usurpation (Constantine II, 767); by election following a prior selection falsely judged as invalid (Clement VII, 1378); accession after an unwarranted deposition or deportation of the previous pope (Felix II, 355); or double election (Anacletus II, Innocent II, 1130). Yet not all antipopes emerged because of malfeasance or bad faith. Because of the lack of a readily accessible electoral code, there could be confusion as to the requirements for a valid choice. Instances occurred where a pontificate, uncanonical in its beginnings, was validated by subsequent acceptance on the part of the electors (Vigilius, after Silverius's resignation or death, 537)."
It is also worth noting that there has been at least 37 antipopes throughout church history. In the words of Encyclopedia Britannica:
It is also worth noting that there has been at least 37 antipopes throughout church history. In the words of Encyclopedia Britannica:
"The elections of several antipopes are greatly obscured by incomplete or biased records, and at times even their contemporaries could not decide who was the true pope. It is impossible, therefore, to establish an absolutely definitive list of antipopes, but it is generally conceded that there were at least 37 from 217 to 1439. Felix V (1439–49) was the last."
This does not sit well with the Roman Catholic dogma of papal infallibility because if there are two people claiming to be legitimate popes simultaneously, then it is impossible to determine which man has authoritative teaching. Both can officially exclude each other. There exists no infallible mechanism we can use to figure out which man claiming to be pope is the rightful successor.
