Christianity
Rich aristocrat pagans had to join the popular growing movement known as Christianity. From that point forward, Christianity was less about living in the (God/Human) relationship with Christ, and more about performance for the Church.
There wasn't a fall of Christianity. It is still a popular religion.
Christianity is popular because it is The Truth and key to heaven.
Trends come and go, Christianity is at its best when unpopular.
Christianity
America
Judaism started out as more popular, then Christianity was created, and it became more popular.
No, Vans has not yet started becoming less popular with the younger crowd.
Yes, Christianity is the most popular religion in the world, with over 2 billion followers worldwide.
Christianity - and the particular denomination is Catholicism
Christianity