IQ is the wrong term IMO.

IQ is attempting to measure intelligence, and generally (but not always) ignores things like education, ongoing mental load (except for during the test), etc.

Intelligence is generally innate ability, but not what you would see day to day ‘under load’.

What we’re seeing is somewhat different IMO. It’s a decrease in the available executive function/free mental capacity of the population.

Executive function is the ability to synthesize the available information (past and present), and create a plan which produces the best outcome - and then follow it successfully.

Someone can have a very high IQ, and low executive function for a number of reasons - disorder (ADHD), bad nutrition, stressful or distracting environment, having too high a workload, or too much bullshit being thrown at them all the time.

Corruption makes it worse because it means it’s impossible to directly reason about how long something will take, or what resources it will take, without going through a bunch of opaque and situational hurdles. It also means tests and validation can’t be trusted, and it’s more likely the water system will be dangerous/cause disease despite everyone saying it’s ok.

It burns executive function and decision making ability.

Extra complexity of all kinds does, but bullshit is one of the worst.

SA had an evil, but competent gov’t so for folks ‘within the system’, things were relatively straightforward and worked as expected. That freed up a lot of executive function to do even more things that worked effectively.

With corruption and BS (aka say one thing, the other thing happens) everywhere, it burns more executive function and everything starts to rot everywhere else too, because everyone starts to get more and more expensive on the executive function side, just to stay alive.

Rather than just driving to a place, for instance, everyone has to figure out if it is going to go through a place that will get them killed (and /or kidnapped and raped).

Rather than just have working water, they have to spend effort figuring out if they need their own supply, how much to keep, when it needs to be rotated or treated so they don’t get sick, etc.

Same with power now, etc.

Often, societies end up stratified into layers based on available executive function. Being rich allows someone to help educate their kids and shelter them during key years, so they learn how to protect and grow that executive function, and aren’t exposed to as many of the traumatic effects that can hurt it. There is also a genetic factor that clearly shows up (not along race lines, but along family lines - it’s pretty clear).

Eventually, folks lose the plot or get pushed down a level due to external factors or mistakes. People with particular behaviors that fit well to the environment can also move up (unless suppressed) using wealth they’ve accrued due to effective function to continue to perpetuate what they think is important to have more executive function, hence class turnover/mobility.

Having a large swath of oppressed folks (who have had their ability to progress or sustain things that give them high executive function systematically broken for generations) take over for the folks previously maintaining it just for themselves, when those folks also disappear, is going to be a shitshow every time, for at least several generations.