A decentralized communications network is not a bad thing. Cryptocurrency isn't necessarily a bad thing. Decoupling traditional means of control of money (banks) from our money is a good thing. However, those banksters aren't going to let their current wealth vanish without taking action to preserve their wealth.
Cryptocurrencies are no less vulnerable to manipulation than any other store of value you can imagine. If you can manipulate the price of silver, a solid material you can hold in your hand, how much easier is it to manipulate data.
Those that think a decentralized network is somehow manipulation proof just don't understand the ability of big data to penetrate obscurity by complexity, nor the immense gulf in capability between the real possessor's of the greatest fortunes in the world and the rest of us.
It might even be trivial for such actors to just buy the entire network such cryptos are based on, if they don't already own most of it.
Due diligence, diversification, and hard work cannot be substituted for. No secret code, dispersal of nodes, or white papers can replace them, and if you aren't employing them in selecting your investments, you're not investing, you're gambling.