Because the marketcap is lower, that means that if someone buys a lot or sells a lot then the price could change wildly and a lot easier, of course when one person with a lot does this, others follow most of the time, or at least stop loss type of stuff gets activated, these all mean that we could see wild movements very quickly. This is why I believe that we can't really make it work all that easily, we should probably consider getting higher ranked coins so we can do a lot better with volatility.
It is about how bookies or whales manipulate prices to make a profit. Coins with a low marketcap are very easy to manipulate. But not all projects can be manipulated by whales because if there is no liquidity then it will be useless. But volatile markets will still occur and that's how markets work. Altcoins can fly very fast and we cannot predict how high an altcoin will fly. But altcoins are great for short-term projects and most of them are not suitable for long-term projects.