All we like sheep have gone astray;
we have turned—every one—to his own way;
and the Lord has laid on him
the iniquity of us all.
Just like sheep, we have all gone astray. We have all gone our own way. Each of us has chosen our own way of life. We make our own decisions. But the ways that we have gone are ways that are "astray". They are not the paths of life.
God has laid on Jesus Christ the sins of us all. All of our "going astrays" have been placed on Him.