This time, Orochimaru revived them using Hashirama's cells to strengthen the binding power of his jutsu. This brought the Hokages back to almost full power, rather than the measly fraction they were brought back in during Part 1. This effectively caused Orochimaru's intentions to backfire, instead of strengthening the binding power of the technique, it granted them the access to their power they needed to break free of the binding. The fact that it was Hashirama's own DNA allowed him to break free completely, and the fact that Tobirama is Hashirama's brother, and thus related to the DNA, allowed him to resist, but not as much as Hashirama.
In short, he was unable to break free in part one.