Why did god chose Jonah as a prophet?

God chose Jonah because Jonah displayed three amazing characteristics that you and might not possess.

First, we find that Jonah was a listener. He listened to the voice of God. Somewhere along Jonah's lifetime, he developed the acuity to hear God's voice over every other noise in the world. Jonah could distinguish God's voice because he had developed his listening abilities and knew, undeniably, what the voice of the Lord sounded like. God chose Jonah because he could hear God's voice.

Secondly, we find that Jonah was available. Jonah was available to do God's work. Jonah had been available in the past and God new Jonah would clear his schedule and carry out the work of the Lord. God knew Jonah would be available this time and probably more times in the future. God chose Jonah because he was available.

Thirdly, we find that Jonah was not perfect, but very, very fallible. This is actually a very good quality to have, in the Lord's eyes. God does not pick the mighty or the proud, or the skilled, or the learned, or the leaders of this world. He picks people that are willing to let God work in and through them despite their inabilities. God purposely chooses the foolish things of this world because, for some strange reason, He delights in bringing shame to the world's wisdom. God chose Jonah because he was not the "perfect" candidate.