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?
There is nothing much the community can do to whales without causing downsides to the wider Bitcoin community. You'd have to implement some sort of decay or tax on these amounts which would undermine some of the very benefits of cryptocurrency (stability against inflation and general security). Whales in many cases are a blessing, because they are taking a vast proportion out of circulation and unless they are an outfit like Paypal then those coins may never re-enter circulation. If you're interested in seeing your holdings go up in value then that would be a positive for you. There are always going to be hoarders and collectors in the world, so you have to ignore/work around them.