See #1003.
For most, a flood means there is a God who can and will judge this planet. What does a child do when scared? Covers it's eyes and pulls the blanket over it's head to hide itself from what it fears... The blanket vanquishes the closet monster as it were.. But in truth, were there a closet monster, the blanket is no defense and the child is doomed. Yet, you pull a blanket of willful ignorance over your head to hide from your closet monster - God.
And yet many devout people see no physical evidence for a global flood, and abundant physical evidence that falsifies a global flood. Are they hiding from God too?
So what. People will see closet monsters. Whether it actually be a monster or not is quite another thing. When one turns on the light, said evidences tend to disappear. There is no evidence precluding a global flood.
As for what people believe vs. what makes them "devout" that's quite another thing. Belief doesn't = truth. And blind faith is folly.