I’ve only watched this from a great distance but what I saw was: Intel didn’t actually manufacture the chips. That was all TSMC. So Intel’s main thing was chip design. And their designs were all about making the transistors smaller. Around 3nm they started running into physical limits. Competitors started out-innovating them with things like GPU deigns and ARM based chips. End of story. They had their time. They ran x86 into the ground and they are fucking done. They would have had to do 5 or 6 things differently to stay on top, and they did none of those.
They always had their own fabs. Utilising TSMC for their GPU's was a recent thing. For all the mistakes they have done, their GPU efforts are actually noteworthy but you don't even have to compare them to ARM or other GPU manufacturers, just look at AMD, they've been killing it.