There
would be a resource extraction boom. Saying "
it won't happen unless a thing that would definitely happen actually happens" is a weird caveat.
The notion that a non-communist Russia would only develop European Russia and a bit around Vladivostok contradicts all pre-war trends, and runs counter to elementary logic. Here's some relevant maps showing development in OTL:
Anyone with even half a working brain can see the obvious axes of development after a simple glance at these maps. Now, once you take into account how utterly terrible communism is at allocating economic means, and then consider what the USSR
still managed to do, the conclusion can't really be missed. A non-communist Russia would have developed the relevant regions to a far greater degree.
....all that being said, I still don't actually think that the Russian interior would become "more developed than the Raj" (assuming, of course, a Raj that stays intact and continues its own pre-war developmental trends). Nor would such a scenario as this yield the (frankly ridiculous) outcome of massive South Asian migration into Russia. A non-communist Russia would be so much better off that Russia's own pre-war demographic trends would continue. This means that there would be many,
many more Russians. A fair number of
them would be settling the Russian interior.