KittyKatz, clever thinking, astute post. to begin, your "If god is so powerful, why wouldn't he just create everything rather than create one tiny molecule and start this billions of years process?"
Even though God is not bound by time, one could say that creating instantly would be preferable to creating over a period of time. However, I'm sure any astronomer asked the question would prefer that the universe be created over time. Astronomers would be out of business if God had created the universe instantly, because the universe is expanding at nearly the speed of light, so that we can see back in time nearly to the creation event itself. If God had created everything instantly (but kept the universe the same size), and placed all plant and animal life on earth a few thousand years ago, we would see nothing of the heavens, other than the solar system and a few stars. However, Psalm 19 says that the heavens declare the glory of God, so it seems likely that God wanted us to see the entire universe. If He had created it instantly, this would not be possible.
The same logic can be used for the creation of the earth and life on it. Besides indicating that the heavens declare the Glory of God, Psalm 19 says that the firmament shows His handiwork. The biological history of the earth is preserved in the rocks so that we can see the creative handiwork of God in producing life's history. If the universe and earth were created instantly, there would be no history of life to examine, and God's glory would not be visible to us.
In theory, the reason the earth may not have been created until billions of years after the creation of the universe could involve the nature of the universe at its creation. The initial big bang creation event resulted in a universe that consisted almost entirely of hydrogen and helium. Obviously, rocky planets are not possible in such a universe. Heavier elements (including carbon, oxygen and metals) were formed in the nuclear furnaces of stars. Really large stars burn quickly and end their lives in explosions, which distribute these heavy elements throughout the local vicinity. So, rocky planets (and living organisms) were not even possible during the first few billion years of the universe's history. Even now, most stars are metal-poor compared to our sun (determined through spectroscopy). So, the earth was created at one of the earliest possible times in the history of our universe. Although many stars may be surrounded by planets, rocky planets are likely to be at least somewhat rare in the universe (although we are just beginning to collect data to answer this question).
In theory again, God may have waited an additional 4 billion years before creating human beings on earth as the reality is we were created at the ideal time to observe the creation of the universe. If we had been created earlier in time, we would have been unaware of dark energy, leaving in question the ultimate fate of the universe (allowing atheists the out of claiming that the universe might undergo eternal cyclic expansion and contraction). If we had been created later in the history of the universe, Hubble expansion would be unobservable, along with cosmic background radiation, and big bang nucleosynthesis. In the future, scientists will be unable to determine how the universe came into existence, but would assume that it was eternal and static.
The remarkable cosmic coincidence that we happen to live at the only time in the history of the universe when the magnitude of dark energy and dark matter densities are comparable. Observers when the universe was an order of magnitude younger would not have been able to discern any effects of dark energy on the expansion, and observers when the universe is more than an order of magnitude older will be hard pressed to know that they live in an expanding universe at all, or that the expansion is dominated by dark energy. By the time the longest lived main sequence stars are nearing the end of their lives, for all intents and purposes, the universe will appear static, and all evidence that now forms the basis of our current understanding of cosmology will have disappeared.
Though, in the why God created the way He did, you need to understand the purposes for which God created the universe. The bible indicates that the earth was established to accomplish the purposes of God and the purposes of God regarding this creation is first and foremost, designed as a place where evil can be conquered. As for the sun, the bible warns that the second coming will be before man can destroy himself. As the bookie, who is your favorite to destroy human life, our sun, the natural time bomb, or man?