you are stupid for thinking that too.. why would Tobi admit that to Sauske? admitting that to Sauske is like telling him "hey, im the reason why Konoha made ur brother destroy ur whole family and clan"Tobi was clearly embarassed about it after the fact. It's the reason why he didn't mention his involvement in the Kyubi attack on the Leaf village to Sasuke.
Tobi is a manipulator and he has Black zetsu to guide him