Board Thread:Lore Discussion/@comment-4057475-20130710075111/@comment-70.29.89.107-20140827003825

Miraak was defeated AFTER Alduin was banished. I can only assume that giving out masks to dragon priests was Alduin's thing. So no Alduin=no mask. That would also explain why he was not evil like the other priests. He came after the dragon war. for all we know he could have been serving Paarthurnax at that point.