Basically, what crystal violet does to a cell is that it binds with the DNA and proteins of the cell. This is one of the widely used methods for detecting the maintained adherence of cells. This process involves the intercalation of dye which will enable the quantification of DNA, which will be held in proportion to the number of cells contained in the culture.
Any cell that goes through cell death loses its adherence and will automatically be lost from the total number of cells thereby resulting in the reduction in the overall population of staining (crystal violet) in a culture.