This is because your Lord would not destroy the (populations of) towns for their wrong-doing (i.e. associating others in worship along with Allah) while their people were unaware (so the Messengers were sent).
Hayo ni kwa sababu ya kuwa Mola wako Mlezi hakuwa wa kuiangamiza miji kwa dhulma, hali wenyewe wameghafilika.