It is due to geography and demographic mapping.
Ust-Orda wasn't physically neighbored the Buriyatia, thus remained under Irkutsk. Same for Agin Buriyat.
Okay then, so answer me this:
- If geography and demograhic mapping and being physically separated were the problem why Nagorno-Karabakh was not unified with Armenia and why Agin-Buryat Autonomous Okrug and Ust-Orda Buryat Autonomous Okrug were not united with the Buryat ASSR, why then was Kaliningrad placed under the RSFSR instead of the Lithuanian SSR? And why then was Nakhichevan ASSR united with the Azeri SSR despite there being a Armenia between Nakhichevan and the rest of Azerbaijan? And while you are at it, please explain
Shohimardon,
Sokh,
Chon-Kara (or Qalacha), Jani-Ayil, Kayragach,
Sarwan,
Vorukh,
Sankovo-Medvezhye,
Artsvashen,
Yukhary Askipara,
Barkhudarli and
Karki. That's at least
14 detached areas established and maintained during the existence of the Soviet Union disproving the idea that Nagorno-Karabakh could not unified with Armenia and that Agin-Buryat Aut Ok and Ust-Orda Buryat Aut Ok could not united with the Buryat ASSR at any point during the Soviet period.
The idea that they have to be neighbouring in order to be unified is overly simplistic to say the least.
And as shown in the case of the Nenets and Komi (examples you seem to avoid by the way), even if the entities border each other they do not have to be unified.
And as the Nenets, Ossetians, Komi, Armenians and Buryat amply demonstrate the Soviets did
not always put all populations of a single ethnic group in a single entity.
So as I originally said, the idea that the Buryat ASSR would be automatically unified with Mongolia into a single Mongol SSR is not supported by the available precedents. It
could have happened, but was just as likely not to have happened.
1. Tuvan wasn't related to Buryatia. They are 2 distinct mongolian sub-groups.
So what? Are all the groups in Dagestan the same? I was under the impression that you had many distinct groups in Dagestan.
And what then of the Chechen-Ingush ASSR and Kabardino-Balkar ASSR? Are we to assume that the Chechen and Ingush are actually the same and not two distinct groups or sub-groups? And that the Karbardins (who speak a Caucasian language) and Balkars (who speak a Turkic language) are the same group?
2. Between them huge Sayan Mountain not.
According to this logic, everything east of the Urals should not have been in the RSFSR......
3. Tuvan was de-jure part of Mongolia (or precisely part of ROC) till 1944, while Buriya was part of Russian Empire since 1690's. So that's why it is separated.
So since Tuva wasn't a part of the Russian Empire, why then was Tuva incorporated as an autonomous oblast (later ASSR) of the Russian SFSR instead of becoming a Tuvan SSR in it's own right like Estonia, Latvia and Lithuania (which incidentally
were a part of the Russian Empire but were separate SSRs....)?