Intel got caught off guard by the rise of advanced packaging, where AMD’s chiplet design could actually compete with a single die (while having the advantage of being more resilient against defects, and thus higher yield).

Intel fell behind on manufacturing when finFETs became the standard. TSMC leapfrogged Intel (and Samsung fell behind) based on TSMC’s undisputed advantage at manufacturing finFETs.

Those are the two main areas where Intel gave up its lead, both on the design side and the manufacturing side. At least that’s my read of the situation.