Imagine being told in 2001 that America would still be at war in Afghanistan in 2018, and it would not be a political issue. And that CPUs wouldn't get significantly faster than the 3.5GHz one Intel demoed that year. What the hell.
Heat dissipation was becoming a prohibitive issue, with CPUs running as hot as a child's toy oven. This pushed companies like Intel towards multiple cores rather than raw increases in clock speed