That is because Allah would not change a favor which He had bestowed upon a people until they change what is within themselves. And indeed, Allah is Hearing and Knowing.
"Wancan ne, dõmin lalle ne, Allah bai kasance Mai canza wata ni'ima wadda ya ni'imtar da ita a kan wasu mutãne ba fãce sun sãke abin da yake ga rãyukansu, kuma dõmin lalle Allah ne Mai jĩ, Masani."