If I don't start from the beginning, it might be difficult to understand, so I have to ramble a bit more.
To put it simply, at the very start, only Earth 0 was considered Earth; all the other Earths were merely parallel universe colonies of Earth 0.
The pioneer crosser, Oda, was just a cruiser captain from Earth 0. Although he could easily sweep through the Otherworld and rule Earth 0791, that was about it.
With just one Different World crosser and a cruiser, he could dominate a primitive tribe, but to develop this 16th-century backwater Earth and join the Celestial Multiverse trade system of Earth 0, that was virtually impossible.
Therefore, he needed to draw in investors, recruit partners, and take out loans from banks to develop his world.
So, Oda used the intelligence gathered during his campaign against the Legion to contact the Legion-affiliated Eastern financial conglomerates and brought them into the fold.
