Have you considered that the universe is a scary and cold place, and considering it in its true nature does not make one happy?
What makes a child happier: 1.) Believing a magical elf brings presents from the North Pole because of good behavior, or 2.) Understanding that presents come from mom and dad's hard work, and when you hear them worrying about money or fighting over it - you know in some small way you are a part of that stress?
The truth rarely bring happiness, merely a sense of intellectual relief. It also usually creates more questions than it answers, despite any temporary enlightenment. How many of us would ever leave the womb, if given the choice? It is warm and safe in there - and everything is taken care of. But outside that womb is where life happens and things get complicated.
Religion is like the intellectual womb - except this is one you have to choose to leave, and it's scary and takes strength of character to do so.
You can't keep holding somebody's hand their entire life. That's what Christianity does. It protects you from the harsh truth of reality and how you're going to die alone. It gives them a sense of happiness. It's less scary knowing that you're going to paradise rather than knowing that NOTHINGNESS awaits you after you die.