That... is because...

Does the bold sentence mean "the second reason why there is so much Christian iconography in large-scale paintings of Canadian plan is that the Canadian plan for a memorial art gallery went much further than the British one"?

Context:

Christian iconography is particularly visible in the paintings commissioned for Canada’s never-built memorial art gallery. There are two reasons for this subject matter. First, religious practice in general revived in the Great War, conveying meanings understood in a Christian context, which could be effectively translated into art. Second, that so much exists in such massive paintings is because the Canadian plan for a memorial art gallery went further than the British one. And it was British artists who received most of the commissions for the large-scale paintings intended for its decoration.