Usually, when the price falls lower, demand increases, which pushes the price higher. But this does not apply to the descending triangle. Because when the price drops lower, there is no buying pressure. Instead, sellers are willing to sell at even lower prices (which is why we get a series of lower highs). Also below the support level stop orders are grouped by many traders who buy from the support level. The more traders do this, the more stops are formed. And as the market moves from one area of liquidity to another, the price is likely to break through the support level, and when these stops are hit, it will further increase the selling pressure.