Dan asks:
If there were enough supplies (from the three philanthropists) to support Jerusalem for 21 years, why did the siege end after 3 years?
Dan, New York, NY, USA
The Kollel replies:
Shalom Rav,
Bear in mind that the Gemara describes how the zealots set fire to the silos containing the supplies to which you refer, presumably in the third year of the siege.
The ensuing hunger and starvation took immediate effect, and was followed by the breaching of the walls and the destruction of the Beis ha'Mikdash.
B'Virchas Kol Tuv,
Eliezer Chysler