Complex sentence: Revisionism was distinguished primarily from other ideologies within Zionism by its territorial maximalism, while not alone, they insisted upon the Jewish right to sovereignty over the whole territory of Eretz Yisrael (originally encompassing all of Mandatory Palestine).
Split into simpler sentences: Revisionism was distinguished primarily from other ideologies within Zionism by its territorial maximalism. While not the only group to do so, they insisted upon the Jewish right to sovereignty over the whole territory of Eretz Yisrael (originally encompassing all of Mandatory Palestine).