keep in mind, tsunade said if something were to happen, they'd have kakashi. i think he knows kakashi would be a threat. also kakashi was the one who taught sasuke a lot of his stuff and has equal skills such as chidori, mangekyou sharingan, katon ninjutsu (yes kakashi has that ). so most of sasuke's jutsu would be useless against him. but first he'll go for the elders, then danzou, then godaime, then maybe some other leaders or some anbu. plus anyone who gets in the way like they said. and naruto definitely cuz they want the kyuubi
hidan and kakuzu might not have known he was there. they only went there cuz kakuzu wanted the bounty on chikiru. it wasnt to kill all the monks. and he could have still been in konoha.