I think that there are people who hold a very large volume of bitcoins. And they have a strong influence on the price of bitcoin. Unfortunately, the price of bitcoin has become unpredictable. This suggests that there are manipulators
There are really people who hold a large amount of bitcoin that can shake up the market once they buy or dump their coins. Good thing as time passes by, numbers of unique bitcoin users, even holding a few quantity of bitcoin, are increasing resulting in a great numbers. With this kind of changes in the ecosystem, even bagholders dump their coin, bitcoin price can stand the pressure because of the resistance that those others bitcoin holders are doing
The price rise obviously works in the reverse direction
I agree that over time the distribution of bitcoins among users becomes more even (and dumps greatly contribute to this), but at the same time we shouldn't forget that with price growing, more and more people who couldn't before affect the price in any meaningful way now turn into mini whales (in fiat terms) and thus get some power to move the price stronger with their coins. The market price is determined by the balance of supply and demand naturally, and its growth in general is the result of the supply contracting and the demand expanding, which necessarily leads to markets becoming thinner, and consequently, to the effect that I described above