I want to make sure I say that there is a more elemental reason why meritocracy produces a corrupt ruling class and it is this:
Cheaters may almost never win but, given equal opportunity and a large enough competition, the winners are almost always cheaters.
Well, no one cheats because they think if that even if they get away with it they will be worse off. No, they cheat because if they get away with it they will be better off. Cheaters are taking a gamble.
Even if the system is pretty good and the odds are stacked against the cheaters, if there are enough players then some of the cheaters will get away with it, nonetheless.
When they do they will gain an advantage. Now, imagine that life is a series of such competitions played over and over again. Each time some people will cheat and some will get away with it. Each time some will gain an advantage.
If the competition is immense, say it encompasses a country of 300 Million or a global population of 7 Billion, then by the Law of Large numbers some cheaters will be lucky enough to get away with it every single time. This means every single round they gain an advantage and slip ahead of the pack.
After enough rounds the front of the pack is completely dominated by cheaters.
That doesn't necessarily mean that cheating will always mean cheating will always pay off. As the Forbes article concludes, "Lottery players almost always lose, but society’s biggest winners will almost always have made their money in the lottery."