Supply and demand principle always works in short term and long term. The millionaires or billionaires can invest their money in Bitcoin market by buying bitcoins gradually or aggressively in short time but their demand will lead price up. Firstly we must think of how price reacts with massive purchases from millionaires or billionaires and we with our smaller capital can follow those whales. We fortunately can purchase bitcoins and finish our accumulation in shorter time than whales, and we can wait for chances to take profit.
OP can see this point, whales will continue their purchases as with big capital their accumulation can not be done too quickly. We can take advantage of it, and take profit when whales buy bitcoin up.
I am both happy and sad at the same time. I am happy that there are many people here who can see the math behind this and realize that you can't do this, because it would create the price to be so high and marketcap insanely high that we are not going to end up with people being able to afford it, billionaires or not.
Richest 1000 people can get together and still not be enough, richest 10k people can get together and it still wouldn't be enough. And that is even if all bitcoins were on sale, and when you consider that not all bitcoins are all on sale, that means they can't even buy it even if they had the money. So as you can see, it is literally impossible for the rich to get majority of bitcoins, that's just not going to happen.