ذٰلِكَ بِأَنَّهُمُ اتَّبَعوا ما أَسخَطَ اللَّهَ وَكَرِهوا رِضوانَهُ فَأَحبَطَ أَعمالَهُم

This is because they pursued what angers God, and they hated His approval, so He nullified their deeds.