It was designed with a global audience in mind at a time when (to the global elite) Africa and Asia weren't worth considering, and the Americas (including the US!) were of lesser importance. In other words, it was global for an audience who understood "global" to be synonymous with "European".
From a practical perspective - the nearest Uni was St Petersburg - if you had to guess how many comparative grammers of say Russian/Ndebele Russian/Cherokee Russian/Urdu were available in late 19th C Biyalostok? I would go for 0
Yes there are structural reasons that inform Esperanto as a Romance-lexified Western Slavonic - but it is hard to argue that it could be anything but structural - how could Zamenhof personally have chosen different?
