He was a well-educated archbishop and a close friend of Wenceslas IV, who also appointed him Highest Chancellor.
It is believed that the year 1380 was a fundamental turning point in the life of the archbishop. He is said to have been affected by the plague, but it was probably some form of epilepsy caused by encephalitis, which led to a radical transformation of his personality. The initially secular-prone and refined clergyman became an intolerant strict ascetic, who refused any form of discussion when it came to some specific topics.
Jan of Jenstejn then started promoting his way of life, which he thought should be adhered to by the whole Czech population including the king. This behavior had fatal consequences. The high nobility gave its support to the archbishop, leading its proper fight against the king through
him. The two former friends became irreconcilable enemies and the situation reached the point when the archbishop started leading his own foreign policy, which was an unacceptable situation for the king (Jenstejn supported the Roman Pope against the Pope in Avignon, while the king wished to remain neutral).
The quarrel kept escalating in the course of the 1380’s until its culmination in 1392-93, when Jan of Nepomuk, the vicar-general and a supporter of the archbishop, was tortured to death. Jan of Jenstejn complained to the Pope in Rome, who was however realistically aware of the fact that he needed the support of the King of Bohemia so he didn’t hear Jan’s complaint. In the end, his own Chapter set against the intransigent archbishop and he had to resign in 1396. He eventually died in Rome, alone and broken.
