Usually most of the ppl is trading when the market is up. The smart guys buy when alt coins are bleeding. It depnds on many other factors
It does not mean that when the market is down people won't do trading, some of these traders knows how to handle the market even if it is declining by looking at the statistics on the chart. I tell you it's so stressing to do it specially if the fluctuation is very low and yes it is the basics of trading to buy low and sell high.