I believe that the reason the earth and the light from the stars appear old or mature is because God created them in a mature state. I take my theory from the creation of man and woman as they were created in mature state.
Yes, Adam and Eve were apparently created as young adults. But the reason to consider the Old Earth Young Civilization hypothesis is not to reconcile science and theology, but to reconcile the Bible to itself. For example, it helps us understand the Hebrew text of Genesis 1:2, ( read literally it says, “but the Earth became …” not and the Earth was …”) the creation of Satan and the Angels mentioned in Job 38:1-7, Isaiah 14:12-14 and Ezekiel 28:12-19, and the fact that in Isaiah 45:18 the Lord appears to claim that He didn’t create the Earth as formless and void (literally an uninhabitable ruin) as Genesis 1:2 is usually translated. Thankfully, it’s not a salvation issue but rather one of curiosity.