Short answers, pulled from the story.
The year 1378 marked the beginning of a crisis that fractured the Catholic Church when two men claimed to be the true pope. One resided in Rome and the other in Avignon while their supporters chose sides based on political loyalty rather than spiritual conviction.
The Council of Constance convened between 1414 and 1418 to finally resolve the dispute over the papacy. It succeeded in ending the schism but also declared its own authority superior to that of the Pope.
Marsilius of Padua published Defensor Pacis in 1324 to challenge traditional church structure by arguing that the universal Church belongs to the faithful not just the priests. He insisted that Jesus alone is the head of the Catholic Church.
Pope Pius II issued the bull Execrabilis which formally condemned conciliarist principles as heretical doctrines holding General Councils superior to the Pope. This action represented a systematic theological counter-argument developed by church leaders against the movement.
The Fifth Lateran Council ran from 1512 to 1517 and confirmed papal teaching authority through condemnation of conciliarism. This outcome marked a turning point where institutional power reasserted dominance over reformist movements.