God sends Isiah becuz the people of Judah have become corrupt.

Ah, sinful nation, a people loaded with guilt, a brood of evildoers, children given to corruption! They have forsaken the LORD; they have spurned the Holy One of Israel and turned their backs on him.

“The multitude of your sacrifices— what are they to me?” says the LORD. “I have more than enough of burnt offerings, of rams and the fat of fattened animals; I have no pleasure in the blood of bulls and lambs and goats. When you come to appear before me, who has asked this of you, this trampling of my courts? Stop bringing meaningless offerings! Your incense is detestable to me.

The people were going through the motions. They weren't doing it from thier heart. But since God knew, it was even more awefull than if they hadn't done it at all i think.

Though your sins are like scarlet, they shall be as white as snow; though they are red as crimson, they shall be like wool.

The coolest part of this story is how God is not only willing, but he wants to. God is soooooo forgiving, and that's cool.