Monotheism during hardship vs. prosperity

وَإِذَا مَسَّ ٱلنَّاسَ ضُرٌّ دَعَوْا۟ رَبَّهُم مُّنِيبِينَ إِلَيْهِ ثُمَّ إِذَآ أَذَاقَهُم مِّنْهُ رَحْمَةً إِذَا فَرِيقٌ مِّنْهُم بِرَبِّهِمْ يُشْرِكُونَ

And when adversity touches the people, they call upon their Lord, turning in repentance to Him. Then when He lets them taste mercy from Him, at once a party of them associate others with their Lord,