That is because Allah would not change a favor which He had (8:53)

﴿ذَٰلِكَ بِأَنَّ اللَّهَ لَمْ يَكُ مُغَيِّرًا نِّعْمَةً أَنْعَمَهَا عَلَىٰ قَوْمٍ حَتَّىٰ يُغَيِّرُوا مَا بِأَنفُسِهِمْ ۙ وَأَنَّ اللَّهَ سَمِيعٌ عَلِيمٌ﴾
[ الأنفال: 53]

8:53 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.

That severe punishment is because when Allah favours a people, He does not take it away from them until they change themselves from their pure state of faith, righteousness and gratitude to a bad state of disbelief in Allah, sin and ingratitude – Allah hears the statements of His servants and knows about their actions; nothing is hidden from Him.

That is so because Allah will never change a grace which He has bestowed on a people until they change what is in their ownselves. And verily, Allah is All-Hearer, All-Knower.

phonetic Transliteration

Thalika bianna Allaha lam yaku mughayyiran niAAmatan anAAamaha AAala qawmin hatta yughayyiroo ma bianfusihim waanna Allaha sameeAAun AAaleemun

Abdullah Yusuf Ali - Translation

"Because Allah will never change the grace which He hath bestowed on a people until they change what is in their (own) souls: and verily Allah is He Who heareth and knoweth (all things)."

Safi-ur-Rahman al-Mubarakpuri

That is so because Allah will never change a grace which He has bestowed on a people until they change what is in themselves. And verily, Allah is All-Hearer, All-Knower.

Page 184 English transliteration