Nobody within the Leaf village could have stopped Obito at that time. Minato couldn't defeat him which makes me doubt the 3rd would do any better. Also at this time im sure the Leaf would want to keep this incident confidential seeing as other village's would capitalize on there weakened state and crush them. Hell they lost there jinchuriki and there hokage forcing old man 3rd to come out of retirement.or all the villages wont let it happen so easily
Because the nine tails has to be sealed last. Doesnt anyone read the manga anymore?he had like 10 years to teleport with kamui and steal naruto,question is: why didnt he?