Your point has one tacit component that you failed to mention. If what you say is true, then before "taxation of the rich and the highest-earners in general was massively lowered" occurred, the concentration of wealth stayed constant. So, if we've now reduced the transfer from the rich to the power a-la the taxes you mention, then that must mean that before, and now after, wealth has always been naturally (if you want to use that term) flowing towards the already rich.
> If what you say is true, then before "taxation of the rich and the highest-earners in general was massively lowered" occurred, the concentration of wealth stayed constant
Actually, it only means that with that taxation system, the concentration of wealth was slower than without that taxation system.
Regarding the wealth "naturally flowing towards the already rich", define "naturally".
