The success of Intel very largely depended on one single thing: volume. By owning most of the PC market, Intel could spend a lot of money into R&D. Which affected both chip design resources as of course manufacturing. For many years, Intel used to have at least one step advantage in the manufacturing process, often more. This is how Intel basically killed all non x86 based processor designs. Most of which were considered technically better, but on inferior processes lost the competition with Intel (I am thinking about all the famous RISC-architectures).

AMD could leapfrog Intel from time to time with a really clever design, but struggled to keep up in manufacturing. This is where the Zen2 gets so dangerous to Intel, a very good design produced on the better manufacturing process. Where did that process come from?

That leads to the decisive point to where Intel is today: the emergence of the smartphone. The impact on Intel is twofold: first of all, the PC market is shrinking as the smartphones are the computing device many people use, PCs have lost their importance for many, even if people still have a PC, they don't get updated as often any more. And secondly: there is a new huge market for semiconductors.

Which Intel managed to not be a part of.

The volume of the mobile marked helped TSMC to get to the point, where their processes eclipsed Intel. This benefits all the competitors of Intel to compete not only on even ground, but on higher ground. Suddenly, non-x86 architectures, mainly ARM become economically feasible. When Apple designs the Apple Silicon, they can afford to throw enormeous R&D resources at any problem. Not only because Apple is a rich company, but also, because the spending is spread across over 200 million iPhones per year. Not counting iPads and soon Macs. This is, why I am so excited about Apple Silicon. For the first time since the passing of the classical high-performance RISC vendors, a non-x86 architecture enters the desktop market, this time backed by huge R&D spending and a superior process.

Is all lost for Intel? Certainly not, Intel still owns the largest part of the PC market. While the problems with their 10nm process were huge, they are not too far behind TSMC, as the 10nm Intel process isn't that much behind the TSMC 7nm as the numbers would suggest. But their moat consisting of volume and process lead has been breached, so success is no longer automatic and Intel needs to work hard going forward.