Primarily, I'm wondering, if Luther's life is butterflied away, along with his personal ideas, how inevitable does any eventual 'Protestant' movement become? I'm given to understand that by the time of Luther, there already was serious discontent in the Church, and there had been some fairly well known and serious movements even beforehand (I can only really think of Hussites off the top of my head, but I imagine there were many). However, given that Luther is effectively considered the father of Protestantism, how likely is it that Protestantism as a whole develops to the same scale and strength as OTL if the events surrounding him are butterflied away? And, if it does rise to the same scale, how long a "gap" would be the maximum before it truly is completely "inevitable"?
The only way I could see avoiding the Protestant Reformation is if you had a series of national churches that owed only nominal allegiance to a figurehead pope in Rome. So they're all still Catholic but they could believe radically different things.
That's one condition.
The other condition is that the Curia and/or the national churches would need to avoid badly abusing the immense prestige and authority they had in the Middle Ages. So, basically, abolish human nature.
That said, avoiding the Babylonian Captivity and having the papacy dial down its political pretensions somehow would at least help.