ordinances for the deceased? does this tell us that mormonism is the only religion that will be relevant after death?
no edward, they do it because they received a revelation from God. perhaps this is what makes them more relevant after life.
The mormon practice of baptism for the dead is taken from a single scripture verse. No other group practices this ritual. It makes the mormons neither more important nor the one that will be relevant after death.
Mormons have a number of odd practices; this is just one of them.