There's a lot to this article, but one interpretation of it is that it is a story somewhat similar to China's— a history with communism and gradual opening-up to private capital and the global market. In the case of China, capital has entered due to its huge export market. In Kerala there seems to have been an important capital injection from remittances, and a growing tourism industry. The article summarizes it as such:
> In short ways, four forces of change – Kerala’s reintegration with the global economy, remittances from the Persian Gulf, strong welfare policies from a legacy of Leftist government, and private investment from individuals and businesses who shared the remittance flows – have combined to form the structure of Kerala’s miracle of human wellbeing with economic growth.
I don't think they'd call themselves ex-communist. The ruling party is the Communist Party of India.
Also, to be clear, it's a common understanding in Marxism that capitalism is a stage of socialism. The "capitalism and socialism are opposites" rhetoric is too simplistic.
Socialism is different but built upon capitalism, in a similar way, for example, to how electric cars are different but built upon gas cars. Marxism opposes neoliberalism and other forms of governance that leave capitalism unchecked, but doesn't reject everything about capitalism— "just the motor, gas tank, and other harmful parts" you could say.
> In short ways, four forces of change – Kerala’s reintegration with the global economy, remittances from the Persian Gulf, strong welfare policies from a legacy of Leftist government, and private investment from individuals and businesses who shared the remittance flows – have combined to form the structure of Kerala’s miracle of human wellbeing with economic growth.