Roman Phoenix: Pre-TL question on Butterflies

In a timeline I am currently working on for a successful Byzantine Empire, John II does not die in 1143.

How much would butterflies from there get out of control by 1200?

Obviously some things will change, but it seems odd that - for instance - Eleanor of Aquitaine and Louis would be happily married until their deaths if they had never gone on the 2nd Crusade (or if it had gone differently).

It could happen, but it seems unlikely to happen just because this changed (and the impact of John being able to continue his plans.

Or for instance that Persia would remain in Seljuk hands because of a different fate for the Seljuks of Rum.

That might be less unlikely. But I don't know, hence asking.
 
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