What triggered landslides in Kerala as per experts?

Dr M Rajeevan, ex-secretary of the Ministry of Earth Sciences, said increased soil moisture due to rain in Kerala may have triggered landslides. He added human intervention may have played a part as thick forest cover was replaced with commercially viable plantations. Indian Institute of Tropical Meteorology's Roxy Mathew Koll said monsoon patterns have become erratic, triggering landslides.