You could have simply omitted the second paragraph and your argument would actually be more forceful. I agree overall with what you say.
I don't think the problem is with how fast Bill Gates' money is increasing or whether the money is being hoarded. "Hoarding is bad" - some folks say this is a somewhat dubious economic proposition because in theory hoarding reduces the overall cash supply with fewer currency units chasing the same number of goods and services. This is actually really good for savers until the hoarding exceeds a certain threshold where it starts interfering with the velocity of money and all that good stuff. (and frankly, the US GDP is something like 18 trillion, the M2 money supply is apparently 10 trillion, and Bill Gates, despite his enormous pile of money, does not even have 1% of it. I don't think he would make much of a dent even if he hoarded every single penny).
The real problem is the propagation of unchecked power. Be it governments. Be it corporations. Be it dictators or whatever. At least, in theory, well designed governments already include checks and balances. Even the most corrupt banana republic is rarely beholden to the power of such a small group of people like we have in the top tech companies. I mean, how the fuck does Microsoft have the temerity to sneakily upgrade OSes even if people don't want to? Why is there no lawsuit against them of any significance? (And I am sure you can find equally bad examples of abuses of power from all the tech giants).
And while we were all told that competition is supposed to cause the checks and balances and will prevent power from accumulating in any one business - it is probably time to ask if that actually holds true in the technology sector, especially at the bleeding edge? It is probably time to legislate the dismantling of these tech giants.