I disagree. Intel was stagnating with the Pentium 4. They needed a shift in design. Why? Because the Pentium 4, the Prescott being the greatest example, is a CPU architecture based on high clock speed. The problem is that above 3Ghz, they were pushing the electrical components near their physical limit. Intel looked ahead and realized they wouldn't be able to push the clock speed of their CPUs much further. Even though their 3.8Ghz Prescott was a monster, it produced insane amounts of heat, and didn't provide proportionally more performance than lower-clocked AMD chips (as we all already know, AMD CPUs could do the same work at 1Ghz slower clock speeds). I think the Core Microarchitecture was a much needed shift. Intel would be in serious problems if it hadn't abandoned the NetBurst architecture.
Pentium 4s were fas but inefficient monsters, true titans of speed that were slowly being crushed under their own weight.
Pentium Ms, on the other hand, were designed with efficiency in mind from the start, because they were laptop CPUs. Intel realized that slow & efficient beats fast & inefficient, even when it comes to desktop computing. Hence, they based the Core architecture on the Pentium M.