If every leaf falls by the decree of God, the commandments make no sense...

If God controls everything — even which leaf falls and exactly where it lands — and if the wind does not blow by chance but only because God moves it, then it is not the wind that makes the leaf fall. Each leaf falls by God’s decree. On that view there is no freedom of choice, and everything is predestined. Every movement of an animal is preordained and no one has the power to do or to refrain from doing anything. 

But then there is no point to revelation, or to the Torah’s commandments, which assume we can choose. That is why this picture is not the rational Jewish view. Free choice is foundational; without it, command, reward, and punishment lose their sense.

Something to keep in mind as we read this week about God creating the world. For more on the Torah’s view of hashgacha see the Rambam in MN 3:17.