The fact the universe from its very inception require certain very specific characteristics in an incredibly narrow range for planets, stars, solar systems, galaxies and the chemicals and conditions for life to exist.
There's nothing to indicate they are variables at all and vary at all. In fact, we've never seen characteristic of anything that wasn't contingent on other physics.
And a God does not need these specific characteristics to allow for the natural creation of planets, stars, solar systems, and galaxies, chemicals, or the right conditions for life. A God could just make that happen directly. Some land, make it the right temperature, poof life alive, and you're done! These special conditions are those which we have that allow for natural forces to result in exactly the universe we have, without God. This universe looks exactly like a universe would need to look if there were no God, and this is exactly true on every level and on every point. It's massively good evidence for atheism because on atheism we would assume these things would need to be the case and lo and behold they are. The fine-tuning argument in this light is really just looking at the fact that the universe can exist without a God, that it looks exactly as if there is no God, and says, "Well isn't that an amazing coincidence? Isn't that too good to be true? Yes it is, God did it!" -- It's saying that it's amazing that there are no gaps to shove God into, and therefore God.
The fine-tuning argument here is wrong because, God doesn't need *ANY* special conditions or characteristics. Only atheism requires that those characteristics should be exactly like they are, because these are the kinds of characteristics that could allow a universe to exist, if God didn't exist. "Why if you jigger those characteristics a bit you might not get 70 sextillion stars and 13 billion years to allow random mindless forces to get have life kick up here and there purely by chance!" -- YOU DON'T NEED THAT! GOD CAN MAKE ONE PLANET AND PUT LIFE ON IT!
You don't need just the right stars to make higher elements in those stars and allow them to explode and make the debris for planets to coalesce. God could just make these higher elements, without the right levels to build them in stars. Only atheism needs it to happen by mindless natural forces. "Oh, it's so suspicious that the universe so perfectly fits what it would need for atheism to be true, therefore, clearly, God exists and did that. Here's some things somebody else pulled out of their ass to suggested if they were different the universe wouldn't exist!" -- If the universe were made out of butter rather than elements there'd be no life, therefore Elves made the universe exist out of atoms. If gravity pushed rather than pulled there'd be no life, praise be to the flying spaghetti monster!
If the universe cannot be explained perfectly by natural forces, then God. If the universe can be explained perfectly by natural forces, "Well isn't that remarkably perfect?" Therefore God! The fine tuning argument is basically saying that perfectly meeting the requirements implied by atheism, is too perfect and therefore is evidence of God. There's a very narrow window of universes that can create themselves without God, and we perfectly fall into that window! It's an amazing feat that only God could do.