This is not so difficult to understand. Those who had fought for what they called the revolution maintained a great pride: the pride of being on the correct side of the front lines. Ten or twelve years later (around the time of our story) the front lines began to melt away, and with them the correct side. No wonder the former supporters of the revolution feel cheated and are quick to seek substitute fronts; thanks to religion they can (in their role as atheists struggling against believers) stand again on the correct side and retain their habitual and precious sense of their own superiority.
But to tell the truth, the substitute front was also useful to others, and it will perhaps not be too premature to disclose that Alice was one of them. Just as the directress wanted to be on the correct side, Alice wanted to be on the opposite side. During the revolution they had nationalized her papa's shop, and Alice hated those who had done this to him. But how should she show her hatred? Perhaps by taking a knife and avenging her father? But this sort of thing is not the custom in Bohemia. Alice had a better means for expressing her opposition: she began to believe in God.
Milan Kundera, Eduard and God