I think a psychologist would say that if you really can’t find common ground, it’s best to agree not to talk about it.
Indoctrination is highly effective. Your parents were raised in a place where toeing the line is the norm and questioning those in power is traditionally a great way to ensure you disappear. Russians are deeply indoctrinated when compared to western nations because that’s how their society has been set up since 1922. The Soviet leadership ruled by suppressing any dissent, violently and without remorse. Just because the Soviet Union no longer exists, doesn’t mean their ways of doing things disappeared too.
The only way to change them would be to engage in an equally sophisticated program of indoctrination: deprogramming as it’s called. Since you lack the resources of the Soviet Union, it would be a much more difficult task, especially since your parents are now older and their brains are less changeable. They were indoctrinated as children and by a very prolific system. Reversing that now, by yourself, is a tall order.
I’m sorry your parents were failed by their leadership, it’s truly a shame.
It’s very simple: human emotion. When something upsets the status quo, people get scared, angry and desperate. They turn to whatever solution they think will fix things.
In the case of nations, that becomes right-wing politics. Many factors in the recent past have caused distress and fear. People are afraid of losing what they have, they don’t like the uncertainty. They lack the education and critical-thinking skills to choose the best course of action, instead they choose the most reassuring course of action.
In 1930s Germany, support for extremist political parties (not just the NSDAP) surged due to the desperate times they were experiencing. Germany underwent a period of hyperinflation, which was followed shortly after by the stock market crash of 1929. They were already in poor shape, both economically and emotionally, due to the punishments meted out by the Versailles treaty.
Things became very bad for the Germans, and they turned to the looneys who offered a solution. A similar scenario is playing out in several countries around the world, especially the US. COVID really upset a lot of people, none more so than the overly emotional and uneducated. They felt attacked and vulnerable, and they were already deluded by years of misinformation. They turn to politicians like Trump, because he appeals directly to their emotions. He makes them feel safe, largely by scapegoating groups who aren’t actually a threat (sound familiar?).
People don’t check if what they’re hearing is true, they care most about having their fears assuaged. This is why we’ve seen a resurgence of right-wing extremism globally.