Intel should have split 15 years ago, ideally, but I'm not sure that splitting now isn't better than not doing it. If they fail to catch up to TSMC, it's possible that the manufacturing branch will drag the design branch down with it.

If they split, it's likely the fab side of the business will need a large infusion of cash in order to catch up (be it in the form of a government bailout or something else), or then they have to accept becoming a second-rate player. For which there is still a large market, so they might actually do decent-ish there. But that pretty much leaves TSMC in a monopoly position.