Why do people think God can't do this?

If he is as magical and whatnot as it is said he is, Of course he can make a rock heavier than he can Lift....he can do whatever he wants, therefore it can be Done. and no he wouldn't be able to lift it, because he Decided that it was so heavy he couldn't. it was his Decision and making. If he wanted to unmake it, then he probably Could do that as well. why do people act like it's such a mive paradox, he'd just DO IT. who said God was physically strong either. maybe the rock just needs to be like 300 pounds.