This because of FUDS. Other holders are on panic to minimize their losses not knowing coins will recover soon. This the effect when you jump in when everything is skyrocketing and suddenly drop. This is normal in this industry.
Fud and fake news is a big influence these days why people are panic selling their crypto investment.
Honestly before even here in forum its happening until now they use the social medias and blog news to spread the fake news about crypto and they heard the bad news sooner or later the price slowly decreases and the awesome thing if they heard the good news about altcoin or cryptocurrency expect the price is getting increasing back..
For me this is normal because there are lots of competitors and every each of them are making bad news just to down other crytocurrency.
Its just like in business online and they wanted to get rankup to the first page in search engine (SEO) you should make a move to rank down the other competitors and start making a bad news just to rank down your competitors its just like in cryptocurrency..
So for me its a normal that we are seeing selling altcoin sooner but there are other people are stay strong holding their altcoins..
Also there are day traders which is doing buy now and sell soon but it gonna affect the market they are investing in new coin mostly and sell soon because the price is increasing when other buyers are keep buying..