Lets say I had a few hundred million dollars that I wanted to buy crypto with. If I bought it all at once, or with a few large buys, it would drive up the price of whatever cryptos I chose to buy, or at the very least, hold them up.
But that's stupid money.
When you have that kind of money, you don't just go to an exchange, you have a group of people intelligently buy crypto for you, at the lowest price possible, and a group trade a portion of it to lower the overall price, and increase the amount you have, all the while carefully buying more and more, and increasing your amount of crypto for trading and holding. For that much money, you could have your own personal team of buyers and traders. Even if you were stuck with traditional trading platforms like Binance, you can buy hundreds of thousands of dollars of crypto at every point where it hits the lower line of the bollinger bands, and then sell portions above them to buy lower.
Any Forex trader, with a bit of practice, can trade crypto, so it's not like you couldn't get capable traders from Wallstreet.
So, yeah, if a billionaire wants to invest in crypto, they can easily buy millions in crypto, even in just a few days if they want, and not affect the market. Someone that doesn't know how to trade can spike the market, or someone that carefully makes their buys can cause the price to go up, but they don't have to. There are likely tons of people that have bought millions in crypto as it's been going down. There may have been even billionaires that have made huge investments in crypto. Technically, they could get a huge portion of the market, and they don't even necessarily need to drive it up while doing so, because they would likely sell portions back with every spike and move up, and then just get more lower.
But when you have stupid money, you can have your buyers working on Bitrex, Binance, etc, as well as Local Bitcoins, etc, and OTC, and through private sales, etc, etc, etc. This huge group of places to buy from means that it's even easier to not effect the price while you are making huge buys.
You could probably have a team buying for you and pay for them with just the profits from the buying and trading they're doing, and still end up with way more money than you started with, without doing anything yourself.