40% of all Bitcoins are owned by just 1000 individuals.
This gives them a disproportionate amount of control over the market as they are able to dump them at anytime.
This is not to mention the high proportion of bitcoins held by miners and exchanges, who may have perverse incentives to ensure that as many people buy up bitcoin as possible and hold it for long enough for the price to rise.
Is there any way to deal with the high degree of centralisation that Bitcoin has?
You can't do anything about it. Probably 1000 people own most of the world wealth too so It is not surprising that something similar is happening with btc. That's called capitalism. And the opposite where everybody shares everything would be communism. If everybody had the same amount of money, either everybody would have Ferrari's or nobody would have any cars. Some people must be poor so some others can be rich. That's how it works.