Mongolian culture and history has been formed in large part by the dynamic forces of nature and struggle that are embodied in the ancient nomadic existance of the Mongol peoples.
Traditionally, Mongols practiced Shamanism, worshipping the Blue Sky. However, Tibetan Buddhism (also called Vajrayana Buddhism) gained more popularity after it was introduced in 16th century.
In 1989 when communism was starting to fall elsewhere, many Mongolian weren't really ready for the change.