It's funny that you managed to win URV3, but not the Fatimid UHV2.
Here, I reloaded and did it again, this time in 1246, 5 turns after Seljuks collapsed.
Did you settle GP and the Relic at the same turn?
EDIT: it finally triggered in 1123.
EDIT2: I reloaded to 1105 and got it to trigger in 1114.
Seems like the time-limiting factor for this URV is really the presence of Friendly Crusader states, not the Cathedrals.
It appears the game forces friendly attitude for vassals, even though they are not really friendly - that's why it didn't trigger. After those extra turns diplo bonuses kicked in. Might add an extra condition, like "friendly or vassal". Just to be sure, ever seen a vassal that shows up as Pleased or worse?