If you've ever wondered how science works, start with the concept of theory, followed by variables, followed by facts.
A good theory will try to explain as many facts as possible. So if two theories A and B are used to explain facts, and theory A explains 100 facts, and the other theory B explains the first 100 facts and another 50 facts, for a total of 150 facts, naturally then Theory B is better.
Or is it.
If Theory A uses 4 variables, and theory B uses 8 variables. Then A is the simpler theory and B is more complex. So is A better than B now? If A cannot explain the other 50 facts that B can explain, then B is still the better theory.
Suppose Religion can explain 100 facts. Religion in the guise of God can explain 100 facts. But religion without god cannot explain the extra 50 facts. So is God necessary to explain what is happening?
Let's look at some facts: the earth orbits the sun; objects fall at the rate of 32 feet /second squared. There are 24 hours in the day. Light travels at about 186,242 miles per second. Now everyone of these facts were not known at one time. But they became known over a period of time using scientific investigation. Religious investigation did not offer up these facts at all. So would you know these facts if you believed in God? No you wouldn't. Believing in God does not make you more knowledgeable of any fact. You still have to enquire about how the came about using a scientific methodology. Believing in God does not help your quest. Only Science does.
So from the stand point of Occam's razor, you don't need God for any theory to be valid or invalid. The theory must stand on its own merits.