All coincidence and happenstance.
..if you believe you can place watch parts in a box, shake it up and open it to find a perfectly assembled watch
Maybe you meant to put a sarcasm tag in there, but I have another reason.
God.
He made it all. He wanted us go forth and multiply. He told Abraham his progeny would be like the stars in Heaven, like the sand grains on the beach.
Over billions of years, He made it all, for us.