Here is how Diance Moczar in Seven Lies About Catholic History sums up:

Galileo,
however, seemed to have little sensitivity to the delicacy of the issue, and he
went on the offensive... [He] related in a letter how he had dealt with the
controversy at a dinner party in a fashionable house. “I commenced,” he
boasted, “to play the theologian.” Were his enemies using Scripture against
him? He could interpret Scripture too, and he would demonstrate that in fact
Scripture supported him and not his opponents. Thus Galileo claimed the right
to decide what Scripture means in the light of his unproven theory...
Then Galileo publically humiliated
his friend Pope Urban by publishing a fictional debate between characters supporting
Galileo’s views and a fool (“Simplicio”) who supports Aristotle, making it
clear that the fool personified the Pope.
Galileo had very publically thrown down the gauntlet by claiming
theological authority and dismissing the Pope as a simpleton.