AHC: Crusader order seizes the papacy?

What if a Crusader order such as the Knights Templar became sufficiently pissed off at pope to kill him, sieze control of Rome and install one of their own to rule the church? What is the best way for this to happen? What would be the historical consequences of such a coup?
 
Anti Pope would be my guess. With such open act said order is excummunicated, their property outside Rome seized and their members arrested and executed. So I guess Templar Pope would be anti Pope, being illegal.
 
I doubt it would last, while there were a few overthrown popes, I really dont think any of the kings would ever allow something like that to happen, and as powerful as the military orders were at their height, they would never be able to handle a single state attack, let alone all of them. I would guess that most of the kings would order the council of cardinals to reelect the pope and murder/excommunicate the orders
 
+ 1 we´d see another anti Pope.

But what would happen if the the head of the order (or another member) is elected by the cardinals
 
About the only circumstance I could see this happening would be one where the Pope does something unbelievably politically idiotic like openly converting to Islam or whatever. Other than that, no way.
 
Something unbelievably idiotic like declaring "Crusader aren't actually doing god's work and aren't actually guaranteed a place in heaven regardless of what previous heretical popes have claimed"?
 
They succeed. Temporarily, but the next pope disbands the order in question after his installation with imperial backing.
 
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