Why are the western slopes of the Western Ghats covered with thick forests and not the eastern slopes?

The Western Ghats cause orographic rain by facing the rain bearing moist winds to rise along the western slopes of the Ghats. Thus, the western slopes get heavy rain i.e., more than 250 cm and remain wet throughout the year. Therefore. tropical rain forests are found in this area which is covered with thick forests. On the other hand, the eastern slopes do not get heavy rainfall compared to the western slopes. Thus, the eastern slopes of the Western Ghats are not covered with thick forests.