Back then when Orochimaru did his edo tensei, he assumed full control over them, but now Kabuto has worked on the Edo tensei in other to allow them have their personality and full power. So when Orochimaru came back, he took the power and every experience that Kabuto had.
And I bet you also know that Kabuto was using Orochimaru's chakra to strengthen the bind the Edos, but now that Orochimaru is back, he is currently inside Zetsu's body and since Zetsu has the same cells as Hashirama Senju and he is using Zetsu's chakra to bind the Edo tensei even more to make it stronger, it is easy for Hashirama to resist it because it his own chakra... also, his life force is huge so that jutsu cant restrict him especially when he is summoned at almost full power state... The rest of the Kages could have come out of it if they were summoned at full power e.g. Tobirama could have come out of it cos he made the jutsu to start with... However, even though Hashirama is not at full power, his life force is enough to over power orochimaru and also when oro tried to strengthen it to restrict him, he is using Hashirama power... it is like using a cup of water to stop a river, the river (Hashirama) will swallow that water from the cup and over power it. So Orochimaru needs to be very careful
