2 Samuel 20:9, “And Joab said to Amasa, ‘Is it well with you, my brother?’ And Joab took Amasa by the beard with his right hand to kiss him.”
Why did Joab kill Amasa? Because he had been replaced by him.
2 Samuel 17:25, “Now Absalom had set Amasa over the army instead of Joab…”
Why did Amasa trust him? The answer is found in the same verse.
2 Samuel 17:25, “…Amasa was the son of a man named Ithra the Ishmaelite, who had married Abigal the daughter of Nahash, sister of Zeuriah, Joab’s mother.”
Amasa was his cousin. Joab killed his cousin because he wanted to be in charge of the army.
“Power tends to corrupt and absolute power corrupts absolutely.” Abraham Lincoln