Relatability
He chooses flawed people because that is who we can most identify with. We relate to those people. We can’t relate to the holy and righteous Pharisees…no, but we relate to Peter though.
He chooses flawed people because their flaws make them see their need for a Savior.
He chooses flawed people because they have no cause to boast. They HAVE to rely on grace. There’s no question, when you are flawed, that it was GOD who did the work THROUGH you and not you on your own!
God chooses and uses broken people to show us that He can equip anyone to do His work. We can look at Moses and see that we don’t need to be a great speaker or a skilled leader to do God’s work.