Because you see, I think that it is easily proven that there were many 'dispersed' jewish people. Yes, they mainly lived in Israel, and the capital was Jerusalem, but there were also many Jewish communities in other areas of the world, for example, in Ethiopia.

There are jewish people in Ethiopia who claim to have been there since Solomon married Sheba. They have, and always have had, the Jewish Scriptures. They are the same as the ones that existed in Jerusalem.

There was a community in Persia, who claim to have been there since the Babylonian captivity. They also have the same Old Testament.

There are jewish people in Egypt, Syria, Turkey, all who say the same thing, and guess what, no complaints about having an edited version of the Old Testament.

It is the same Bible. It is the same Book of Isaiah, which is nearly identical - 97% - as the one in the Dead Sea Scrolls.