Sure Christianity has just one god, but there is an awful lot of different versions of him
Are Mormons Christian? They say they are, many other Christians say they are not.
One of many reasons: They don’t do the whole Trinity thing.
According to the LDS Church, God and Jesus are separate, distinct. Father and Son yes, but in a literal sense, not as distinct manifestations of the same thing. Holy Ghost is a totally distinct entity as well.