Shitcoins with small marketcap or centralized cryptocurrencies can surely be controlled by pump and dump groups or main investors. However, I don't believe this holds for decentralized cryptocurrencies with huge marketcap, like bitcoin or ethereum. Blockchain wallets show that funds are very diversified, and it's rare to see some 'big' holder sell coins. I think what affects the market most of all these days is news. People then consolidate over the news and start buying or, more often, selling coins massively in the matters of hours. To overcome it, we need the crypto community to expand and become more mature.