Ibn Kathir (Abridged)
Hafiz Ibn Kathirوَنُقَلِّبُ أَفْئِدَتَهُمْ وَأَبْصَـرَهُمْ كَمَا لَمْ يُؤْمِنُواْ بِهِ أَوَّلَ مَرَّةٍ وَنَذَرُهُمْ فِى طُغْيَانِهِمْ يَعْمَهُونَ (And We shall turn their hearts and their eyes away, as they refused to believe therein for the first time, and We shall leave them in their trespass to wander blindly.) (6:110),فَلَمَّا زَاغُواْ أَزَاغَ اللَّهُ قُلُوبَهُمْ(So when they turned away, Allah turned their hearts away.) (61:5),فَإِن تَوَلَّوْاْ فَاعْلَمْ أَنَّمَا يُرِيدُ اللَّهُ أَن يُصِيبَهُم بِبَعْضِ ذُنُوبِهِمْ(And if they turn away, then know that Allah's will is to punish them for some sins of theirs) (5:49). It was said that the meaning of the phraseثُمَّ كَانَ عَـقِبَةَ الَّذِينَ أَسَاءُواْ السُّوءَى(Then evil was the end of those who did evil,) is that evil was their inevitable end, because they rejected the signs of Allah and made fun of them. This is the view of Ibn Jarir, which he recorded from Ibn `Abbas and Qatadah. Ibn Abi Hatim also recorded it from them and from Ad-Dahhak bin Muzahim.
This is the apparent meaning -- and Allah knows best -- of the phrase:وَكَانُواْ بِهَا يَسْتَهْزِئُونَ(and made a mockery of them.)