“his own stated admission that he broke from his own mesorah to support Zionism”
He realized his own mesorah was wrong, and adjusted appropriately. His father had done so decades earlier, working for Mizrachi in Poland and then for what became Yeshiva University in the US. Rabbi Yisachar Shlomo Teichtal, the author of *Eim HaBanim Semeichah*, realized it too, but unfortunately he did not survive the war.
Today most Religious Zionist rabbis come from either the school of Rav Soloveitchik z’tz’l or Rav Kook z’tz’l. They differed on a lot of things (including the nature of Religious Zionism!) but agreed that a Jewish state in the Land of Israel is a good thing. They met once, in 1935, and Rav Soloveitchik, who wasn’t yet a Zionist (he was on the Moetzes Gedolei HaTorah of Agudath Israel of America) would praise Rav Kook tremendously then and later. It should be noted that both were on excellent terms with many non-Zionist and even anti-Zionist rabbis in America and Eretz Yisrael.