Complex sentence: For years many progressive Catholics harboured hopes that he himself might eventually ascend the papacy, but when John Paul II died most commentators believed that his election was unlikely, given his liberal reputation and apparent frailty.
Split into simpler sentences: For years many progressive Catholics harboured hopes that he himself might eventually ascend the papacy. However, when John Paul II died, most commentators believed that his election was unlikely, given his liberal reputation and apparent frailty.