Federico Faggin made possible the microprocessor by replacing fast metal gates on transistors with slow gates made of polysilicon. Low and slow finds its roots in the very physics of solid state, separating the microcosm from the macrocosm. Chips consist of complex patterns of wires and switches. In the macrocosm, the rule was economize on switches, squander on wires. But in the microcosm, all these rules of electromechanics collapsed.
Wires are the problem.
However fast they may be, longer wires laid down on the chip and more wires connected to it translated directly into greater resistance and capacitance and more needed power and resulting heat. These problems become exponentially more acute as wire diameters drop. On the other hand, the shorter the wires the purer the signal and the smaller the resistance, capacitance and heat. This fact of physics is the heart of microelectronics. At the quantum level, noise plummets and bandwidth explodes.