I don't have any insider info on this, but here's my guess:
Gelsinger thinks x86's days are numbered. So Intel's historical moat of designing and manufacturing x86 chips is going away.
So now it's more compelling to treat design and manufacturing as separate business concerns:
- For potential foundry customers, it reduces fears that Intel will give higher priority to fab'ing its own chips.
- It frees Intel's chip designers to design chips without needing to assume they'll be built at Intel's foundries. E.g., they can design chips for TSMC's process if that would result in a better product.
And given all these factors, I suspect Gelsinger and the Intel board of directors are planning to separate the design and manufacturing functions into separate businesses. (Either practically speaking by limiting their interaction within Intel, or literally by making them separate companies.)