Why was Leiden University founded after the siege of Leiden?

The University of Leiden was founded in 1575 by William of Orange as a reward for the citizens of Leiden for their bravery during the Spanish siege of 1574.12

During the Dutch revolt against Spain, the city endured a grueling siege from May to October 1574. The townspeople successfully resisted the Spanish forces, eventually securing relief when the dikes were cut, which flooded the surrounding countryside and allowed Dutch ships to bring necessary provisions to the starving population. Following this victory, the establishment of the university served as both a tribute to the city's resilience and a strategic move to create a center for Calvinist theology, science, and medicine.231