why does Jesus allow his followers to walk away?

JESUS ROCKS!

Christ predicts that He will be left alone and comforts them with the knowledge that they will abandon Him but He will not be alone. This is actually in Chapter 16. God would force no man to defend Him or remain to give his life for the One who was giving His and that is what would have happened. Only one of them put up any kind of resistance and rebuked for it. Everything that happened leading up to His sacrifice was orchestrated by Him. Make no mistake. At anytime Christ could have freed Himself and gone another way.

One of the key elements of God's plan for all of us, His children, is the principle of agency. God will not force us to obey Him or to follow His gospel. We must choose by ourselves to follow and obey. Thus, it would be contrary to Christ's purpose to force His disciples to remain with Him. Those that walk away from Christ, will eventually repent of their actions and acknowledge their mistake. If they sincerely repent of their action, they will be forgiven. However, repentance also includes faithful obedience thereafter. So our faith and our works are coupled together to determine our eternal reward.

Because Jesus was a pathetic excuse for a person

As a test to prove unto themselves whom they had chosen to serve.

he doesnt allow it he gives us free will to do whatever we want

Because that would prove it's a cult