A lot of lesser known altcoins have very few people participating in them and thus either has most people buying or most people selling. That is actually how you see those rapid crazy 100% gain and 100% loss charts: if everyone is buying...of course the price goes up.
Variations in buying coins are always in the market so that everyone who buys it always happens at different times and also on different coins so it is not easy to increase the price in the market because now the choice of coins is increasing and everyone is not buying at the same time.