Did they really need a study to figure this out? If all it took to be rich was to be intelligent, high IQ societies like mensa or triple nine would be social groups of the richest of the rich. Instead, you have everything from unemployed housewives to celebrities to garbagemen and everyone in between claiming membership. If intelligence was the sole determining factor, or even much of a factor at all, people like the Kardashians would not be millionaires. The reality is that the only thing that one needs to be wealty is luck. Being in the right place at the right time, whether it's by being born to wealthy parents, being born with a particular set of genes, meeting the right connections, or even just reading about something called bitcoin in 2009 means that you're significantly more likely to live a life of luxury.
I haven't read this entire thread, but I'm sure that somebody has brought up examples of geniuses who have acquired vast wealth, and used those as justifications for their belief that meritocracy is real. Here's something for these people to ponder: would Bill Gates be a name synonymous with ultra-wealth if he'd been born 100 years earlier? Would Michael Jordan be a name known by people in all corners of the world if he'd been born in Burkina Faso? Would Warren Buffett be who he is if Benjamin Graham hadn't influenced his life?
"There but for the grace of God, go I" sums it all up pretty well. God, luck, fate, whatever you want to call it, is something that is outside of anyone's control, and it dictates a heck of a lot more than most people are willing to admit. Who we are as individuals, the actions we take or don't take, and even the thoughts and emotions that we have are the result of a countless number of factors that were outside of our control, let alone monetary wealth.