Single half a case, market manipulation(Pump and Dump). This is the host activity that changes the value of the Altcoin
The mode of operation of this scam involves two cycles. The most seasoned, they buy cheap altcoin, then, they start spreading rumors to increase the trading volume and value of Altcoin. After Altcoin has reached a desirable price, they will start the second cycle by selling out, even dumping, causing the market to fall.
To avoid being a victim of this trick, you always need to set goals that you want to achieve, for example 25%. In case you can not check daily transactions, it is best to place a limit order. A limit order is executed when the price reaches the limit.