I'm still wondering why the first didn't break out of Edo the first time orochimaru summoned him
Current hashirama was brought this time with almost his full power. In other words in part1 hashirama's power is so low.
Current hashirama is like madara they can't be control.. I remember that madara stated that "there's a risk of this jutsu, as long as you know the seal you can realese the ET. An undying body (zombie), unlimited chakra cannot be control.."
More or less it means the risk of this jutsu is as long as you know the seal you can realese E.T (like itachi release every edo tensei). But undying body + unlimited chakra can't be control.. Which is makes sense that Y kabuto never control madara.. Same goes to hasirama who almost had his full power.. Undying body + unlimited chakra = can't be control..
It says unlimited not infinity, unlimited can't be finished like water in the sea (so huge), infinity is like space in univers or numbers..