medieval-religion: Scholarly discussions of medieval religion and culture

(An) apallingly ignorant question(s) for the learned members of this list:

My impression is that in early Christian (including Byzantine?) iconography,
the focus was on the Resurrection and/or the kingship of Christ, but that at
one moment,  in western Europe at least,  the emphasis began to shift to the
Passion and Crucifixion (with a somewhat lesser interest in the Incarnation
and the events in the life of the Virgin Mary). Is this impression mistaken?
If not, when and where did the change occur? and why - popular piety,
crusades, mendicant preachers?  and what about iconography in Eastern
Christianity?