I live 30 minutes away from Vezelay, so your question interested me.
This is not my own answer but one I found on the internet which may help you.
Interpretation of the Tympanum
The tympanum of La Madeleine de Vézelay is different from its counterparts across Europe. From the beginning, its tympanum was specifically designed to function as a spiritual defense of the Crusades and to portray a Christian allegory to the Crusaders' mission. When compared to contemporary churches such as St. Lazare d'Autun and St. Pierre de Moissac, the distinctiveness of Vézelay becomes apparent.
The historian George Zarnecki wrote, "To most people the term Romanesque sculpture brings to mind a large church portal, dominated by a tympanum carved with an apocalyptic vision, usually the Last Judgment." This is true in most cases, but Vézelay is definitely an exception. Unlike its contemporaries, which tend to depict the Second Coming of Christ, the subject of Vézelay’s tympanum is the Pentecostal Mission of the Apostles. Its tympanum reflects its unique importance in the development of the Crusades.
Thirty years before the Vézelay tympanum was carved, Pope Urban II planned on announcing his call for a crusade at La Madeleine. In 1095, Urban altered his plans and preached for the First Crusade at the Council of Clermont, but Vézelay remained a central figure in the history of the crusades. The tympanum was completed in 1130. Fifteen years after its completion, Bernard of Clairvaux chose Vézelay as the place from which he would call for a Second Crusade. Vézelay was even the staging point for the Third Crusade. It is there that King Richard the Lionheart of England and King Philip Augustus of France met and joined their armies for a combined western invasion of the holy land. It is appropriate, therefore, that Vézelay’s portal reflect its place in the history of the crusades.