This 'takeover' is imaginary. What happened was that people who were sick of libertarianism and techno-utopianism (in some cases because it wasn't the first time they'd seen those ideas wax in significance in the bay area) began to vocally push back and argue that many of the ideas of libertarianism and techno-utopianism are flawed. I suspect you'd also find a pretty close correlation between intensity of left-wing rhetoric and economic insecurity due to rising rents and other factors.