Itachi was the only thing keeping Obito in line for part one & two.
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Obito was the one to flee from Itachi.
The only movie
written by Kishimoto pretty much shows this:
Itachi shows up to rescue Sakura and immediately realizes that physical attacks won't work:
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[/SPOILER]
Itachi says he knows a way to hurt Obito in spite of Kamui:
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FYI, constantly keeping his distance is how Obito kept even Kamui a secret from Itachi.
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He kept it a secret from no other ninja...
Obito thought Itachi was THE SHIT, bra.
Obito was constantly amazed by Itachi...
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Conclusion:
Obito was incredibly, incredibly cautious of Itachi & kept his distance
He was too frightened to send Pain to destroy the leaf while itachi was a live so knowing that kakuzu and hidan wouldnt be able to harm the leaf he sent them to die
He even stayed out of Akatsuki when Itachi was roaming.
(So Madara Orochimaru and Obito have that in common.)
