If you believe the universe is a reflection of its Creator, it would be meaningless to ask, 'Why was the universe created?' or 'Why do we exist?'
When you look in the mirror, do you ask: 'Why does my reflection exist?' Of course not! Why would you ask such a pointless question? Your reflection exists because you exist. Similarly, the universe exists because He exists.
So to ask 'Why does the universe exist?' it is the akin to asking 'Why does the Creator exist?', which is the same as asking 'Why is the Creator the Creator?'