This is because they said to those who hated what God has sent down, “We will obey you in certain matters.” God fully knows their secret conspiracies.
ذٰلِكَ بِأَنَّهُم قالوا لِلَّذينَ كَرِهوا ما نَزَّلَ اللَّهُ سَنُطيعُكُم فى بَعضِ الأَمرِ وَاللَّهُ يَعلَمُ إِسرارَهُم
zaalika bi annahum qaaloo lillazeena karihoo maa nazzalal laahu sanutee’ukum fee ba’dil amri wallaahu ya’lamu israarahum