And the CCP actively denied climate change as a means for the West to stop their modernization until the last decade or so.

Industrialization was a priority for most Marxist-Leninist based states because that was considered the best means of both defending themselves from the "NATO aggression" and, in theory, increasing quality of life.

It's a relatively recent trend that ecological conservationism and climate action has become a major actual leftist talking point. Obviously you could find individuals who were concerned but the governments are largely M-L and simply didn't care that much compared to building industry.