How knowledge actually disappears
It is not pulled out of anybody.
إِنَّ اللَّهَ لاَ يَقْبِضُ الْعِلْمَ انْتِزَاعًا، يَنْتَزِعُهُ مِنَ الْعِبَادِ، وَلَكِنْ يَقْبِضُ الْعِلْمَ بِقَبْضِ الْعُلَمَاءِ، حَتَّى إِذَا لَمْ يُبْقِ عَالِمًا
Inna-Llāha lā yaqbiḍu-l-ʿilma-ntizāʿan yantaziʿuhu mina-l-ʿibād, wa lākin yaqbiḍu-l-ʿilma bi-qabḍi-l-ʿulamāʾ, ḥattā idhā lam yubqi ʿāliman
Allah does not take knowledge away by pulling it out of people. He takes knowledge by taking the scholars, until when He has left no scholar behind,
Where this comes from
It ends: people take ignorant men as leaders, and they are asked, and they answer without knowledge, and they go astray and lead others astray. Nothing is removed from anyone's head. People simply die and are not replaced.
The full narration
Narrated `Abdullah bin `Amr bin Al-`As:I heard Allah's Messenger (ﷺ) saying, "Allah does not take away the knowledge, by taking it away from (the hearts of) the people, but takes it away by the death of the religious learned men till when none of the (religious learned men) remains, people will take as their leaders ignorant persons who when consulted will give their verdict without knowledge. So they will go astray and will lead the people astray
Source
Ṣaḥīḥ al-Bukhārī · 100
- Agreed upon as authentic (al-Bukhārī / Muslim)