It has not come back at all

Can you please explain what is "it has not come back at all"? I believe it refer to a tradition... many thanks

"Oh, the Mongols sacked Baghdad and so that's why it all ended". If that were the only force operating, then later when the Islamic culture rose, you would still see this tradition of scientific innovation, but it has not recovered! it has not come back at all! compared to what was going on in that three hundred years. And what you do, is you read the writings of Al-Ghazali, who is a Muslim cleric, and he was to Islam what St. Augustine was to Christianity.