أَلَمْ تَرَ إِلَى الَّذِينَ أُوتُوا نَصِيبًا مِّنَ الْكِتَابِ يُؤْمِنُونَ بِالْجِبْتِ وَالطَّاغُوتِ وَيَقُولُونَ لِلَّذِينَ كَفَرُوا هَٰؤُلَاءِ أَهْدَىٰ مِنَ الَّذِينَ آمَنُوا سَبِيلًا
“Have you [O Prophet] not seen those who were given a portion of the Scriptures yet believe in jibt and taghut and reassure the disbelievers that they are better guided than the believers?”
Revealed exposing the Banu Nadir's telling the Quraysh that they were "more rightly guided" than the Prophet ﷺ and the believers, during the formation of the Ahzab.
This is the specific asbab al-nuzul: classical tafsir (e.g. Ibn Kathir) records Ka'b ibn al-Ashraf's words to the Quraysh -- quoted in the post -- as the occasion for this ayah's revelation, condemning those who call disbelievers "more rightly guided" than the believers.