If you read Jeremiah, God always promises there will be a remnant.
Gen_17:7 And I will establish my covenant between me and thee and thy seed after thee in their generations for an ***everlasting*** covenant, to be a God unto thee, and to thy seed after thee.
True, a few folks have remained.
Now then; was that enough to balance the fact that MOST of the Jews did NOT hold up their end of the bargain?
Genesis 18:32
And he said, Oh let not the Lord be angry, and I will speak yet but this once: Peradventure ten shall be found there.
And he said, I will not destroy it for ten's sake.