If we take Jango's word for it, he says he was recruited by a man named Tyrannus, or Darth Tyrannus, or Count Dooku whichever you prefer. Dooku used the recently deceased Sifo-Dyas's name to order the army and recruited Jango as the template. Since it is known for certain that Dooku was in on Palpatine's plan to start the war, it would make perfect sense for Jango to still be in Dooku's corner even once he starts playing the role of separatist leader. When Padme started making a big fuss in the senate to keep an army from being form, Dooku called upon Jango to assassinate her, who at that point was staying on Kamino, just as Lama Su said, presumably to continue to provide fresh genetic material for the creation of more clones. When Obi-wan tracks Jango to Kamino, Jango makes a beeline back to Dooku on Geonosis, presumably to warn him that the Jedi are onto them.