“fairly quickly”
Imagine the US trying to wean itself off natural gas.
I don’t think John Kerry would think it could be done by December 2022.
We can’t say 2030 is impractical and then say 2023 is practical.
By this winter they will be partially weaned off natural gas. A little of this, a little of that, and conservation measures, and they will muddle through pretty well. These are rich and resourceful places. Russia however has permanently lost a huge market, that it cant easily substitute because of the geographical and infrastructure constraints of natural gas. This all is a permanent economic disaster for Russia.