There are too many altcoins and each market is very small. In some cases even a single person can cause a huge price change with a relatively small amount of money. In case of btc, it is not so easy, because it is the biggest market, which is also one of the reasons why btc price is less volatile. In case much more money comes to crypto, price will not only grow, but should also become less volatile. Only the biggest whales will be able to cause sudden price movements.