An East-West Reformation

Thid history is dependent on two changes in European history. First, Jan Hus did not go to the Council of Constance and thus was not burned at the stake, allowing him to keep his movement from splitting and to spread both into Poland and Hungary and east into what was not yet Russia. Thus the Protestant Reformation happens a century earlier and divisions are along East-West lines rather than North-South.

The second change happens with another person not dying when their supposed to, in this case Henry V. He lives another 25 years is easily able to squash Joan of Arc and consolidates France and Britain into one realm instead of leaving a one year old child as king. Instead he has three children and the pious and scholarly Henry is persuaded to abdicate in favor of his more politically and martially inclined brother Richard-Louis I on Henry's death in 1447. In return Henry is made a bishop and extracts a promise from his brother to lead a crusade against the eastern heresy.