CRP and LTW Levequests give 3000 experience reward after reaching level 50 in class

[Suirieko]

It's probably intended because you reached level 50.

Whenever you reached level 50, any EXP from level 50 or lower contents have been drastically reduced, (Which includes the Ixali). This is designed to discourage players from using old contents for level 50 or higher, thus forcing them to use the Heavensward's Contents.