There are some questions in life that have no earthly answer to be found, but the answer lies within God's ways and thoughts that are above ours. Sometimes we seek love, acceptance, trust, and favor from others, when only God is the one we need to ultimately please and provide those things. Sometimes we place blame and hurt on others, instead of giving the forgiveness that God never denied us of.
'God will deal with and defeat the devil at some point in time.' Leave it to God to avenge your wrongs, as He can do way more than you could even dream of. We aren't meant to know all the why's that we come up with, but we can trust in His Word and the victory He has promised.