Makes sense about the salt being too valuable to use to contaminate ground, but they did effectively destroy the city: Homes were burned, the people enslaved and shipped off, the walls were torn down, and the harbour destroyed. None were really rebuilt after.
Although the city technically still existed and was technically still inhabited, it was effectively a near-ghost town until its complete abandonment later on (I think a century or two).
Rome, IIRC, also poisoned the wells, so that likely contributed to it, too.