In Christianity we do find the same problem as in Judaism having different faith groups all claiming that they are the right Jews or right Christians.
Rabbi Eliezer Silver who visited a displaced persons camp after the war, encountered a Jew who told him he no longer wanted anything to do with Judaism.
He explained that there was a Jew in the camps with a siddur that he would share only with those who were willing to give up their daily slice of bread.
Why are you looking at one disparity in the difference of custom between Ashkenazi and Sephardi Jews rather than the astounding number of similarities they share?
The differences are so negligible that they just prove the rule – we are one people with one Torah. Jews are forbidden by the Torah to eat or even own leavened products on Passover.
We should remember that God took His People out of Egypt to make them one nation, united by the Torah. The Jews should take this at heart and should know their common history and their common goal.
Some eat rice, some don’t, and it matters not. We are one family, the children of Israel.
Also the Christians living all over the earth should know that there are differences depending on where they live and what season it is. Most important is that they do not take part in pagan traditions, like the Easter bunnies a.o..
What Is Group Evolutionary Strategy?