Lamentation 4

Lamentation 4:6

For the iniquity of the daughter of my people
Is greater than the sin of Sodom,
Which was overthrown as in a moment,
And no hands were turned toward her.

Sodom is generally considered the most sinful city of all time.  There's never been anywhere else that God specifically decided had to be destroyed, to prevent contaminating the rest of the world.  But He did decide that there, and obliterated it with no survivors except Lot and his daughters.

Now, we're told that Jerusalem was worse?  That's quite the charge to level, but He is qualified to make that decision.  So if it was that bad, is the only reason He didn't obliterate it as well the protection he had promised the Jews as part of the covenant?