Dude it's not even about change, hashi was always the strongest in kishi's mind. Kishi did not want to reveal god like strength in part one, he made us believe hiruzen is as good as it get's which is why he had his fodders praise him. At the end of part 1 kishi gives us a sign that shit is about to get real with the first and madara statues.Dont hiruzen fanboys understand the word ''CHANGE''??? Kishi changed narutos strongest hokage/shinobi 2 eva exist(apart 4rm so6p) from hiruzen to hashi. Just live with it, we're in shippuden, not part 1 so u outta believe shippuden, not a stupidly weak chuunin called iruka.
In part 2 as the characters become older he reveals more of the real deal god like powers. Madara and hashi are on landscape changing abilities. An example of god like powers kishi revealed is nagato now because of him konoha need re drawing. Something kishi did not want to reveal in part 1.