John took a detailed interest in administration, and made effective changes to the way things worked. Partly his interest was motivated by the need to raise money – as inflation ate away at his earnings, and his desire to reconquer France magnified his need. The break with the church from 1208 to 1213 actually helped his need for money, and doesn't appear to have materially damaged his reputation in England
The break with Rome, 1208-1213
Neither John nor Pope Innocent III expected or wanted any trouble. The crisis was sparked by the monks of Canterbury.
When Hubert Walter died, the monks of Canterbury, jealous of their rights, secretly elected one of their number – Reginald, and off he hopped to Rome. John was livid – and forced the monks to elect John de Gray. In all the kerfuffle, Innocent III ending up imposing Stephen Langton on John as his new Archbishop of Canterbury.
Innocent had a clear view of Papal supremacy, as expressed in one of his letters thus:
Now just as the moon derives its light from the sun and is indeed lower than it in quantity and quality, in position and in power, so too the royal power derives the splendor of its dignity from the pontifical authority
However, in practice he would normally accept that the king's consent and approval was also required. The crisis was caused by a rather unfortunate concatenation of events.
John made the most of the crisis. He took the revenue from church lands for a while, and then when he realised he didn't have the men to administer them, made the Abbots and Bishops buy the land back. There appears to have been little reactin from Barons or anyone else to the Interdict and Excommunication. The crisis would only be resolved when other political problems forced John to seek allies.