The early modern period is about 1000 years after the establishment of the Assumption as part of the calendar. In the early days of Christianity, the Church must have had a fight on its hands to get hold of material resources that had previously gone to support paganism or the pagan aristocracy. It would have had to tell people *why* it was taking tithes, so some sort of mass indoctrination would have been required.

By the Reformation, there were so many only-formally-Christian festivals in the calendar, costing so much to put on, that it's easy to see the people who ultimately had to pay for it all thinking "hold on, do we really need this?". Roll on the day when our current established cult gets the same treatment and the mobs start looting sports stadiums and throwing widescreen TVs out of pubs in iconoclastic fury.