Hearing, Listening, Applying

What, precisely, did Yisro hear that got him to come and join the Jewish Nation? Rashi tells us that he had heard about the splitting of the Sea and the battle with Amalek. What was it about the battle with Amalek that drew him to join?
Rabbi Yitzchok Isaac of Komarna explains that Yisro had dedicated his life to understanding God and the spiritual truths of the world. When he got to the point of feeling that he had finally arrived at the truth and the zenith of human understanding he was happily content with what he had achieved and stopped any further pursuit. Then he heard about the Splitting of the Sea and of the great spiritual awakening that had wrought in the Jewish Nation. Nothing, even his own personal efforts at great self-sacrifice could possibly bring greater awareness of God than that which was achieved at the Sea.
And then a shocking thing occured; despite the great spiritual awakening the Jewish Nation had experienced they weakened subsequently leaving room for an Amalekite attack. Yisro realized then that no matter how great his spiritual achievments were, there was no guarantee he could maintain them. He needed to attach himself to the source of spiritual greatness and growth. He went to join Moshe and the Jews in the desert