why did genjutsu suddenly work on him?

I get the aversion from Kabutoro you have, he's kind of trying too much, and he doesn't have any of the qualities that made Orochimaru or Kabuto interesting.

but fuck it, I want Kabuto to win and make a difference, Kill Itachi for reals, and then let Sasuke exact revenge on Kabuto somewhere in the future, or kill both Uchihas, and show them peace like Sai and his brother.