Christianity lasted almost 400 years until its first Schism. Mormonism...?

Actually, there were hundreds of different sects, before the Roman church umed power and started killing all the "heretics". They were just the "last man standing", so to speak. History is written (rewritten) by the conquerers. The Christian church literally fell apart after the death of the apostles. Christians were hunted almost to extinction. They dropped many of their most offensive beliefs in an effort to appease the Romans. The Catholic church came along later, after many of the most precious doctrines of Christianity had been perverted or lost. Then they started enforcing their version of Christianity by the sword. The Mormon or LDS church owes its existence to a gracious god, who decided to send a new prophet to the world, and restore the authentic doctrines of early Christianity, including the poorly understood controversial ones.