Believing God exists is not the same as trusting the God who exists. A nominal Christian often discovers in suffering that his faith has been in his church, denomination, or family tradition, but not Christ. As he faces evil and suffering, he may lose his faith. But that’s actually a good thing. I have sympathy for people who lose their faith, but any faith lost in suffering wasn’t a faith worth keeping. (Genuine faith will be tested; false faith will be lost.)
If you base your faith on lack of affliction, your faith lives on the brink of extinction and will fall apart because of a frightening diagnosis or a shattering phone call. Token faith will not survive suffering, nor should it.