What I want to know is why Hokage was so slow in stopping the summonings!

Orochimaru: Ok, lets summon the dead.

Hokage: hmm, he knows this technique, let me pick my nose while he summons 2.

Orochimaru: 1! 2!

Hokage: Uh oh, I better stop the 3rd.

Orochimaru: 3!

Hokage: *counter summon*