http://www.chabad.org/library/article_cdo/aid/1062884/jewish/Perek-7.htm Korban Pessah Perek 7
The following rules apply when there were many individuals who were ritually impure due to contact with a human corpse on the first Pesach. If they were the lesser portion of the Jewish people, their offering is postponed to the second Pesach like other impure individuals. If, however, the majority of the Jewish people were impure due to contact with a human corpse or the priests or the sacred utensils were impure due to contact with a human corpse, their offering is not postponed. Instead, they should all offer the Paschal sacrifice in a state of ritual impurity, those ritually impure together with those who are pure.
This is derived from Numbers 9:6 which states: "And the men who were impure because of contact with the corpse of a human soul." Implied is that the offerings of individuals are postponed until the second Pesach, but those of the community are not postponed. This concept applies only with regard to the ritual impurity associated with a human corpse, as explained in Hilchot Bi'at HaMikdash.
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He was describing the situation precisly in his time where vast majority of the Jewish people were outside the land of Israel and were ruled under foreign control.
The issue of ritual impurity I brought above, now the issue of the Temple itself not being needed I will try B'H to find the sources from Chazal particullarly from the Rambam which I saw/heard earlier.