You live in a freaking dream world. There are only two possible reasons that Obama failed to renew the SOFA with Iraq. Politicsa and politics. He did what he wanted, he got all troops out of Iraq and in doing so invited the caliphate folks to open up shop. Good Lord man, open your eyes.
I am also aware that, at the time, some republicans like Karl Rove complained that Obama could have got the immunity from prosecution if he had handled it as an executive action, requiring only that Maliki and Obama sign it and leave the Iraqi parliament out of it.
But the Iraqi Parliament approved the SOFA that Bush signed so they needed to approve the SOFA that Obama would have signed.