Who says they didn't do anything? It's possible we will learn about what happened during those 9 years soon.
i just believe they're all dead after Birth by Sleep. i mean there's no reasonable explanation for them relaxing while Xehanort the Apprentice is terrorizing the worlds creating billions and billions of heartless and the entire worlds were in shambles for 9 years.
There are other reasons. Them being dead sounds farfecht to me. It could be that the other masters were fighting the heartless this whole time, but they were fighting them in other worlds that Sora has not been to.
another thing is why the hell didnt mickey do ANYTHING to stop Xehanort? you're telling me mickey couldn't find Xehanort for 9 years? mickey is a keyblade wielder. why did he have to wait for sora to be the next keyblade wielder to actually do something?
and don't tell me its because of the DtD. he didnt visit the realm of darkness till during kh1 and then he realized he needed another keyblade wielder but that wasnt till during kh1 so what the hell was he waiting for 9 years? relaxing?
What would have been the point of visiting the dark realm before KH1? Even if Mickey found the dark realm keyblade it's not like it would do him any good. Mickey had to wait until Sora was chosen to be a keyblade wielder, he had absolutely no choice. Nothing Mickey could have done would have made a difference until Sora came into the picture. Without a keyblade and a keyblade wielder on the side of the realm of light, Mickey's efforts in the dark realm would have been meaningless.
Like Mickey said in his letter to donald and goofy, "We must find that key or we're doomed' meaning even if Mickey had the dark realm keyblade they would still be doomed without Sora.