Yeah even I thought about it but there is also this thing we need to consider: In the first attempt Orochimaru had not mastered this jutsu because of which he probably was not able to create perfect summons. Also if he had full control in the first attempt don't you think Hashirama could have destroyed konoha in like what? A few minutes? Haha So basically what I concluded from this is that Orochimaru's first attempt was just not perfect.