Some say it's basic human behaviors that have become maladaptive in the current resource and energy rich environment. Others feel it's the hijacking of the hyper-social nature of humans into a growth-oriented superorganism similar to certain art and termite species. Ultimately it's the massive increase in raw energy available to humans via the discovery of fossil fuels; this massive expansion of humanity simply could not have happened otherwise.
Find yourself questioning the pro-growth, pro-natalist narratives pushed by the well-funded talking heads? Here are some starting points: