I wonder how ancient history and so many ancient poems are known by modern people.

It is recorded in various documents. In ancient times, it was generally believed that "everything is inferior, and reading is high", so scholars with conditions at home at that time would collect many books. In fact, many ancient wisdom crystals were lost or damaged in the long years, which is very regrettable. What we see now is just a drop in the ocean, but it is precisely because of this that they are particularly precious.