I could say that clouds that look like real things are
real things and are communicating meaning to us. Thus a puffy cloud that looks like a choo choo train is actually a projection of a real train from another dimension.
If I was convincing (and cynical) enough, I could get people to believe it was true and a new trans-dimensional cloud religion (TDCR) would be born. People would begin to see relationships between cloud shapes and real events: "That train that crashed in India last week was predicted in the clouds!" No proof or evidence needed, confirmation bias would take care of the rest.
Scientists would protest in vain that clouds are only water vapor and that TDCR people only "see" things that are culturally relevant to them. Pacific Islanders would never "see" cars stuck in sandstorms, and Mongolians would never "see" coastal cities demolished by hurricanes but we would just rationalize such discrepancies. Most of you can imagine a religion like that catching on and growing popular, although I just now invented it! 
It seems that a strong need to believe in something like a religion
is part of our makeup as humans. But that does not mean that any particular religion is correct, even though it feels that way to believers.
You would think that the scientific research on how prayer and meditation affect the brain would demonstrate this. It does not matter what god a person prays to, or whether they just meditate on nothing. The brain waves are the same. If one religion was true and the rest false, you would expect to see a different wave pattern for the true one--the one that was actually connecting to Jehovah or Vishnu or Allah. But you can't tell any difference.
We have a hard time accepting that we don't know something. We follow the instructions of authority figures like parents and teachers. We also have a hard time changing our minds once we have made them up. Add to that our tendency to create patterns and to see connections where none exist, and you get a strong bias in favor of religious belief.
This bias does not mean that religion is good, necessary or true. In fact, it means that we atheists have an uphill battle convincing people that there is no evidence for any gods, and that therefore most (all?) religions are clearly made up by humans and blatantly false. And we need the rationality of the scientific method even more than ever.