Isidore of Seville ascribes this to his refusal to join the Arian Church of the Visigothic realm in Hispania.
"[2] A more likely reason for John's detention was his lengthy stay at Constantinople, with the possibility that he might be a spy for the Byzantine governors in the far south of Iberia.
After Leovigild's death in 586, John was released and founded a Benedictine monastery at Biclaro (the exact site is undetermined), where he presided as abbot and finished his Chronicle (in 590), before he was appointed Catholic Bishop of Girona under the new episcopal government.
It is the most complete and reliable authority on Leovigild's stormy reign, and on the Visigothic conversion from Arianism to Catholicism.
Three other chronicles cover parts of the Visigothic rule of Hispania: the bishop Hydatius, bishop Isidore of Seville, both of the doctrinally unified Catholic Visigothic establishment, and the fragmentary but apparently secular Chronicle of Zaragoza.