No I studied The Crusades only up to the third one, so their demise never figured into anything I read.
I actually calculated their recruitment and casualties myself. From memory, I figured out that they never had more than 300 knights at a time in the holy land and had 90%+ casuality rates.
The reason was that they almost killed Saladin once by recklessly charging his tent in the morning of the battle, forcing him to flee naked on camel back. So they just did that in every battle and kept dying.
They convinced the last King of Jerusalem to march out to confront Saladin with The True Cross as their standard so they could try the tactic again, and got EVERYONE killed and the kingdom fell.
The previous Crusader tactic, which worked, was hiding behind their castle walls and waiting for Saladin's conscripts to go back home for harvest.
So I came to the incompetent bloodthirsty fools conclusion myself. King of France just got them for being heretics, true or not (probably not), and they no longer had a presence in the holy land for anyone to give a shit about to save them.