when retailers or weak players are selling heavily on bad news due to their fear strong players like operators make the best use of this situation and they are heavily accumulating their positions in selected stocks. 

Once the accumulation by operators is over at the low price level, the market starts gaining rapidly without giving any chance to retailers to enter their positions. On the contrary, retailers keep shoring such advancing stocks which harms them more and more.  this results in a huge loss to them and they keep shorting at lower price levels in the false hope or anticipation of another bear run in that stock or index.

The solution to the above problems is - Buy on Bad News.