Lack of critical thinking is a bit of a worldwide schooling system failure. Underfunding on one hand and not having an education plan for people to develop those skills leads to what we have. Some are lucky to get those skills from home or from top tier schools.
I imagine that this state of things was somewhat beneficial for the ruling elites but Russia is now showing the whole western world, that dumb population is a huge liability.
Indeed it is - and likely by design anyway (critical thinking is bad for political control, after all). You generally want the ones in power (preferably the ones aligned to you) to be better educated than the masses.
In a 'well functioning' aristocracy the rich and titled tend to go to the best universities and get educations an such. In authoritarian governments the opposite tends to happen. Anyone that is too smart could take over and rule themselves and must have an accident before that can happen. You end up circled by ass kissers.
I imagine that this state of things was somewhat beneficial for the ruling elites but Russia is now showing the whole western world, that dumb population is a huge liability.