While he was considered to be a learned man, he was also known for his erratic and often cruel behavior. This combination of intelligence and poor judgment led to him being labeled as a "learned fool."
It's important to note that this title is likely more a satirical label than a historical fact, and may be influenced by the perspective of those who opposed him. However, John's reign was certainly marked by both periods of progress and instability, which may have contributed to this perception.