The short version without breaking out charts, stats, etc is that the different regions of Russia have been carrying the burden of the war unevenly and aren't happy about it. This is why the Kremlin has been careful to not pull too many troops from regions in the caucusus that are prone to seperatist movements (Chechnya and Dagestan specifically). But to protect their pet regions (Moscow-St Petersburg) and their angriest regions (the entire south from Krasnodar to the border with Georgia), they've had to draw more and more working age men away and doing so has pissed off multiple regions that are further away from their centre of power, already receive few if any benefits from being part of Russia, have shit infrastructure, employment...basically fucking everything, it's a 3rd world country in most of it's Asian regions.
The thesis is pretty simple, this war is well into the process of bankrupting Russia. When that occurs, the centre won't have the ability to hold the far flung regions together. The south will probably at least attempt to splinter off into it's own Republic (Krasnodar, Rostov, Volgograd and the Caucusus), the never really far under the surface seperatist movement in the Urals will pick up, and probably pieces of Siberia as well. Basically if you look at central Russia on a map you'll notice that there is a band of cities from west to east at more or less the same latitude as Moscow. Most of those regions are capable of breaking off and supporting their own former soviet republic (like the Stans).
As to why the next 24 months...21% interest rate and rising is leading to a corporate bankruptcy crisis, the central bank is incapable of raising nearly enough funds from bond purchases, 100's of billions frozen in international banks (mostly countries that don't give a fuck what Trump says), rail system data came out yesterday showing 6% YoY decline in freight capability (Russia is very rail dependent for basically everything, so that's a sign of the failing power of the central government to keep it's economic heart beating), and the Ukies now focusing on knocking out refinery capacity (down 12-15% is the best estimate I've seen so far). It's held together with duct tape and Europe can provide enough support to Ukraine for them to continue indefinitely imo.
