If I understand correctly, Intel CPUs around that time were super deeply pipelined so you could meet timing closure at such high frequencies. So yeah you can keep pushing the clock-speeds up and up but now a mispredicted branch really shoots you in the foot. Makes sense at the time because people associated clock speed directly with performance. Higher frequency more better. Intel kinda gave up on that at some point and started over with the core architecture design which has a lower clock speed but does more each pipeline stage.