Judas's betrayal was the very heart of the entire event of Judas.
If God hadn't allow Judas to choose evil, then the entire concept of free will would be meaningless. Judas was God's "tool" because it was Judas' own sad choice to betray Jesus. No victimology here with Judas.
Since God knew the outcome of his choice...how is this a choice for Judas? He could not choose otherwise, could he? God cannot be wrong, can He?