Lack of commitment to the Islamic struggle (jihad)

رَضُوا۟ بِأَن يَكُونُوا۟ مَعَ ٱلْخَوَالِفِ وَطُبِعَ عَلَىٰ قُلُوبِهِمْ فَهُمْ لَا يَفْقَهُونَ

They were satisfied to be with those who stay behind, and their hearts were sealed over, so they do not understand.