The Intel chips of that time were fine but it was a problem from both sides. Apple refused to "compromise" their hardware design and Intel failed to deliver on their promises regarding power/heat budgets and kept telling Apple execs that they were just one cycle away from fixing all of the problems.

Ultimately, Apple won that fight when they decided to stop letting Intel control their hardware roadmap and it's been a great change for the entire industry. Intel is finally seeing some changes in their own products, largely in response to Apple dropping them. Now Nvidia is getting into the game which means more competition which is also good.