Take for example the theory of relativity. In my opinion the most profound insight ever into the nature of the Universe. Great! But how many people actually understand what it is/what it means/how it works? I mean really understand?

Truth doesn't make us happy. Understanding makes us happy- and while one person might have been happy with just "The Universe was created, humans were created, there are forces in the universe greater than the will of man, there are more things in the universe than can be perceived in the spectrum of experience" other might ask "What are the forces in the Universe." or "What created the Universe".

My point being, belief is just the same thing as an understanding. And if a person has a false understanding of the world, that's okay so long as it doesn't hurt someone else because by their very nature understandings change with time and knowledge. So long as time exists understanding will change.

Nobody ever sat down and said "Life is so awful, I'm going to invent a false reality and then trick myself into believing it to make myself happier." I'm pretty sure it's all just been a progression of developing understandings.

No single person has the capacity to understand everything, so inherently every person has false but convenient notions that allow them to understand a thing very superficially, though in a sufficiently practical way. Fortunately, we are all at different levels of understanding for various topics. I say fortunately because this means we get to share knowledge and understanding when the opportunity presents itself to someone who may be able to do the same thing in return for another topic.

The way I see it, people who believe in God aren't so much concerned with their understandings of the mechanics of the Universe, they are much more concerned with the dynamics of their inner psychology or spirituality- with which detailed understandings of the mechanics of the emergence of our Universe are generally accepted as being beyond the scope of human knowledge.