"There is a difference between denial and betrayal.
Judas was of the devil, he was demonic. And yet for three years he participated, and looked, and acted, and talked just like the rest of the disciples to the point they could not tell the difference. He was not a disciple that went bad or did wrong. He was of the devil to begin with. The Lord chose Judas to perform this purpose according to prophecy.
But Peter is another example of the denial of Jesus. He did not betray Jesus, he is just full of pride. Faith did not fail Peter - Jesus kept him the whole time but He did let Peter fail. He let Peter see what he is really made of, and then Peter was later restored.
There is a difference between betrayal and denial."