You know that the RAND Corporation published the blueprint for this in 2019 - titled "Extending Russia", right? 8 of the first 10 measures have been implemented (items such as "Exploit tensions in the South Caucasus"). So the more sensible question is: why is the US doing this, and why would Russia just idly wait for the "Provide lethal aid to Ukraine" measure to be fully executed?

Short answer: the US is more interested in destroying the German economy than Russia's, and starting a protracted war with Russia through a Ukrainian proxy is how that is being done. It is amazing how happily the EU wrecked its economic prospects for at least two generations, to the exclusive benefit of US industry. Russia's actions here are totally rational, not only that but they provided ample warning for years about NATO expansion into Ukraine being an actual red line (as opposed to a lot of the red lines declared by the WH).