It could be easily their cpus architecture, silicon process and technology, company organization, company processes, amount of "none essentials", etc. reached a point pushing Intel into a steep "decline" phase, or something the shareholders would name "a loss of momentum", etc.
It happens in all large companies after several decades of a grow, a success, when the company and its products have passed the phase of "maturity" (see the picture).. The Maturity phase for Intel could be the 25 years from 1990 to 2015, imho..
Btw., 125000 employees w-w is really too much for what Intel is doing, imho. They will go down to some 40000-60000 within next 5 years, my bet (I worked at 4 large w-w corps, 3 of them did the same decline, the 4th will do as well)..
PS: in the graph you may see that typically during the maturity phase the cash/revenue holds, but the profit declines - that is because the companies usually hire more and more employees (usually sales and marketing, management and other none-essentials), and/or they start to dig into the biz areas which are not their core business..
PPS: FYI - AMD
almost tripled the number of their employees since 2016 (to 26000 as of the end of 2023), thus having today 5x less employees with 2x more revenue per employee compared to Intel..