In many religions, God is the ultimate authority and is to be obeyed and revered to a degree that no human authority enjoys in this day and age. (The concept of blasphemy has no humanist equivalent.) From this religious perspective, atheism comes from pride, stubbornness, and egotism; in short, unwillingness to submit to authority – in effect, to the authority of scriptures or institutions which act as a proxy for the authority of God.
I think questioning and ceasing to believe in God does require confidence about defying that authority. But it is motivated by doubt over whether there is any real basis for the authority. To this type of person, the only authority is objective truth, and from this point of view it is also pride and egotism that stops people submitting to authority – the authority of truth. We have been too proud to readily accept that our planet is not the centre of the universe; too proud to accept our humble evolutionary origins. Too pompous to consider the notion that the universe is not in fact a stage set up expressly to play out the epic drama of our human moral struggles.