The verses turn the attention of Muslims to the history of the past generation throughout ages.
The cause of their destruction and ruin has always been their oppression. ``They were oppressors.'' says Qurän. A kingdom may be continued with blasphemy; but not with oppression. It connot keep on unjustly and with cruelty.
The Arabic, ``ZOLM'' translated to oppression, has a wide variety of meanings, including all sorts of sins and guilt. Even polytheism in Quränic literature, is a kind of ZOLM, and the worst kind of it.
As to the phrase:ِ ``BUT THEY WERE NOT TO BELIEVE'' it may imply that God will not perish those who are expected to believe later on, or in future.