Dooku was actually Palpatine’s most valuable apprentice. It was Dooku that could use his unique reputation, wealth, charisma and influence to lead a double life, create the CIS, recruit Ventress, Durge, Grievous and the other Dark Acolytes. Dooku who erased the records in the Jedi Temple, Dooku that eliminated the Bando Gora while also finding the perfect Cline template in Jango Fett. Dooku who helped fund both the GAR and CIS with his almost limitless wealth. He was able to operate with impunity because the Jedi thought he was still one of them, he caused a schism in the Order, turning such notables as Sora Bulq to the Dark Side. It was his training that turned Ventress and Grievous into the most feared Jedi killers of their day. Tyranus understood the truth behind Darth Bane’s vision of using deception, manipulation and the tools of the Dark Side to destroy the Republic and Jedi far more than Maul or Vader ever did. His machinations during the Clone Wars are what allowed Sidious as Palpatine to gather so much executive power and pass the Emergency Acts(of which Order 66 was one) meaning that the destruction of the Jedi Order and the Republic as well as the formation of the Empire owes an enormous amount to Darth Tyranus.