Why did the Christian church cherish and preserve ancient knowledge?

All the churches of the Abrahamic religions have done this. This was necessary to keep the flock in obedience. By the time these religions emerged, mankind had accumulated a significant amount of knowledge. The church hardly shared this knowledge and skills with the flock. Illiterate, stupid people who blindly believe that the church says it is easier to manage. The church spent huge amounts of money to buy and steal ancient knowledge. Example: the seizure of Christian Constantinople by the crusaders and the export of all literature by representatives of Catholic leaders.