The Pentium 4 was intel's Windows Vista moment. Corners were cut, marketing overruled engineering and performance suffered.
When it came out there were still PIII's running noticeably faster.
This combined with the RDRAM fiasco allowed AMD to have a nice run with the Athlon series and break Dell's intel exclusive offerings. It was a big deal at the time. I'm certain that intel was thoroughly embarrassed and rightly so. I doubt it is a mistake they want to repeat anytime soon.