Christians: Can someone explain the literal and spiritual meaning to these verses?

This is a fable designed around the central moral suggesting that the choice of Abimelech as king is a poor one, since not God's man. Its worthless scoundrel has been selected as a ruler. They brought on their own destruction. The fable is what brought on Jotham's curse (see verse 20) which truly comes to p. Its a parabolic fable... you can read more in 2 Samuel 12:1-4 and 2 Kings 14:9-10