I know you won’t like the answer to this, so I won’t try that answer. :-) Instead, let’s use the easy fallback: remittances. Kerala’s per capita, IIRC, is pretty close to it’s significantly more technologically advanced neighbour Tamil Nadu, because it sends its males to the Gulf to work under regimes that are the exact opposite of communist paradise. Kerala, by this argument, gets to eat its cake and have it too.
Also, the CPI in Kerala historically faced a lot more challenge than Jyoti Basu and Co in WB, yes?
—ravi