IMO, Jewish people, especially Ashkenazi Jews, are smarter because they started off at a higher point. The vast majority of those that survived WW2 are those that were able to escape Europe due to their relative affluence or type of occupation as well as those that immigrated to America. These occupations would be tend towards the White-collar class, with higher education as a necessary per-requisite. This situation is a consequence of the Jewish exodus from ancient Israel, with the demographics of the Jews being more kin to Europe than the Middle-East or Asia by the time the Industrial Revolution picks up.
If you want to ask why Ashkenazi Jews are "richer and smarter" than Arabs/Bedouins/Turks, you could ask the same thing with the difference between "White America" and African Americans.
Because of this start, as a percentage Jews are relatively well off compared to other ethnic groups, with a smaller percentage in poverty. The fact they are not in poverty allows them to advance through higher education, compared to those less fortunate. The family of an Arab farmer or pottery maker 50 years ago is less likely to have a better education than the family of a Jewish trader after all.
The gap that widened between Europe and Asia because of the Industrial Revolution is being closed now, at least. This is why, for example, groups like the non-diaspora Chinese and Indians have shown their intellectual potential once they get out of poverty.