There's a much simpler, technical explanation: the transition from linear power supplies to switch mode power supplies, in devices of all sorts including but n

There's a much simpler, technical explanation: the transition from linear power supplies to switch mode power supplies, in devices of all sorts including but not limited to computers. The timing of the peak and beginning decline in per capita power demand coincides with the point at which SMPS's became a practical option for new designs beginning at the end of the 1970's. The decline since then may just be the result of gradual replacement of linear supplies by attrition.