ذَٰلِكَ أَن لَّمْ يَكُن رَّبُّكَ مُهْلِكَ ٱلْقُرَىٰ بِظُلْمٍۢ وَأَهْلُهَا غَٰفِلُونَ
That is because your Lord would not destroy the cities for wrongdoing while their people were unaware.
(This) i.e. sending messengers (is because your Lord destroyeth not the townships) the people of the townships (arbitrarily) because of their idolatry or transgression; it is also said that this means: out of injustice (while their people are unconscious) of the commands and prohibitions and the conveyance of the messengers.