If you buy at the bottom then sell to kill a run, you make a profit and propagate the cycle once more. You could even afford to not sell all of them at the top to help facilitate a continued decline in a stock and manage a decent profit.
No in the long run they make more money by jumping in at a lower price right before or just as the run starts. while witing they can use their money on other plays. Even they know that there is a run about to happen here.
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