South Korea is probably the most advanced of those. But even then the APR-1400 is a modified version of the US System 80 nuclear reactor. It is less advanced than latest Russian reactors which have enhanced safety with core catcher. And South Korea does not have the full nuclear cycle. They do not enrich their own fuel. And they have no fast reactors. France has a more sophisticated nuclear industry than South Korea.
It is hardly surprising that Russia lags in EV-related tech. Batteries have piss poor performance in cold climates. The cold reduces their range. Russia has wide expanses. And heating with electric is way more expensive. So instead they spent more money on natural gas powered buses and things like that. Russia as a major oil producer also has the dino juice that countries who want to move to an electric car fleet typically lack.
Calling it simply a "modified US system 80" is disingenous, APR-1400 is a Gen3+ reactor and heavily modified compared to even the OPR-1000. Fuel enrichment for SK is hardly a technological issue rather than a question of politics. Russia is ahead of SK in nuclear tech but certainly not on the level of "can vs can't" like you implied in the first post.
It does explain why Russia is behind but does not change the fact. Same could be said about the large aircraft like IL-96 - it makes little economic sense for a country like SK to develop such planes when they can buy Boeing and Airbus, there is simply no incentive.
Considering that Russia is also lagging behind SK in semiconductors, electronics and automobiles, then the assertion that there is an incomparable gap between SK and Russia is highly questionable. Russia is ahead in some industries, SK is ahead in some others.