One way to look at this is: the US wants to eliminate iranian backing of terrorists in Iraq. Another way to look at it is: US is starting to roll up iranian cells around the world in preparation for a strike on iran.
I think Iran is itching for a fight. A war is the only way the diminutive one stays in power, but, they need someone else to start it. Our capturing of Iranian's in Iraq is agitating them. I look for Iran to keep doing more bold things like this kidnapping to slowly escalate things, but still maintain victim status. I look for them to do something to Israel very soon. Brinkmanship, Mullah style..