Israel is inherently different from the Diaspora as far as minuy dayanim is concerned. Every city in Israel must have a court to reflect its sanctity and special halachic status. Specific laws like egla arufa and ir miklat apply only in Israel. Kedushas ir is incomplete without the appointment of city and district judges, as a fulfillment of the mitzvah of yerushah v’yeshivah. Diaspora cities, no matter how large they are, have no Biblical obligations that derive from their status as a city. Even if there is minuy dayanim in the Diaspora, it is limited to yashar v’tov, not yerushah v’yeshivah. Hence the requirement for judges in either districts (Ramban) or cities (Rambam).
This is why Moshe integrated minuy dayanim into the story of the aborted march into Israel and the tragic change in Jewish Destiny that resulted from the episode of the Spies. Appointing judges, minuy dayanim, in cities and districts in Israel fulfills two aspects: tzedek u’mishpat and yerushah v’yeshivah.