Addendum:
The Baal Hatnya/Harav/Hagraz and his Grandson The Tzemach Tzedek were Amudei Horoah but not Rabanlm.
Rab Yaakov Z”tl whom you quoted was not a Rav the last 38 years of his life those years when we had the greatest impact.
Rab Aharon Z”tl was not a Rav.