The first I read of the snowball earth theory placed it at the end of the Permian, 230 million years ago. Evidence of deep ice cover is found right up to the tropics in Southern and Western Africa, South America, Australia and India from that period. The argument fell down because they failed to take into accout the continents were in much different positions to what they are now. I think some people just like the idea of catastrophes. The idea may spring from biblical ideas that the world is going to end any day.