How Did the Western Schism End?

At the time there were three claims to the Papacy. There was antipope John XXIII, antipope Benedict XIII, and Pope Gregory XII. The Council of Constance was called and at the council Pope Gregory XII resigned and antipope John XXIII also resigned so that the Church could elect a new universally recognized Pope. Antipope Benedict XIII refused to resign but by this point he had no support from any existing Cardinals. With 2 of the 3 claimants to the Papacy officially resigned, the Council then declared the antipope Benedict XIII excommunicated. The Council then elected Pope Martin V who was universally accepted by the Church.