In 2012, Manmohan underwent operations, never quite recovered physically

Mani Shankar Aiyar reveals in his book how Dr. Manmohan Singh, after undergoing multiple coronary bypasses in 2012, never fully recovered, affecting his governance. Aiyar suggests that Pranab Mukherjee should have taken over as PM, with Singh elevated to President in 2012. Singh's key achievements include MGNREGA, RTI Act, and National Food Security Act.

source https://timesofindia.indiatimes.com/india/in-2012-manmohan-underwent-operations-never-quite-recovered-physically/articleshow/116690400.cms