Obi wan really doesn't need 3 scenes where he still can't figure out where the dart came from or how to find kamino. Not to mention that Kamino and the army being a secret go nowhere.
He's following a trail. Moronic though it may be, it's still in the classicist mystery storytelling mode. The last sentence I of course agree with. Why would you take over a secret army without asking any questions.
If a free lunch doesn't even exist, why would a free secret army exist? :)