Why can't RBs throw it away?

I didn't mind the play. But when it was call was my problem. At the time Bush only had one carrie witch was a busted play that resulted into a TD. So that did not give us any look on how they was going to react to Bush running. The Ravens played Bush different than everybody else. They did not have the whole team keying on him, So thats why Colston was Doubled covered. I think if they would have waited later in the game the play might have worked. Also I am wondering if Bush even seen Colston when he threw it. They might have told him to just throw to a spot.