The LORD had compassion on Jonah. Jonah, can’t you see the Lord blessed you, saving you from the sea. The Lord gave you this plant to comfort you in the heat of the day.
The Lord had blessed Jonah; had shown grace and mercy to him. It would be wrong for Jonah to begrudge the Lord blessing others. It would be wrong for Jonah to refuse to be a conduit of God’s blessings to others, when God had so blessed him. And what’s wrong for Jonah is wrong for you and me.