God created the universe to manifest His glory and all that entails. You can see it in everything. That's the easy part.

I think it is illogical to ask why did God chose to create at this time, because there was no time when God spontaneously outside of time and spaced created all things.

That's as much as we will ever know. If in a trillion trillion years from now no matter what wonderful things man does it will fair to compare to the greatness of God's creation.

To me that's exciting because it tells me we will never stop being satisfied by what God has planned for those who love Him.