we seem to be in a phase of spending trillions on the computer, so while it isn’t likely, it isn’t impossible

There's so much you'd need to scale, it's even more expensive than the humble few billions you spend on a new fab. And, beyond R&D, the scale itself also makes it significantly more expensive. This is an energetic dead end, you would need a country to fully commit to making this one thing.

Lithography is AFAIK the most expensive part. If you wanna scale to larger wafers I'd guess you're talking hundreds of billions and at least a decade. And even then, what will your yield be? Surface area grows to the square of the diameter of a circle, and so will errors. The larger your wafer goes the lower your yield will go, especially if you're going to use the whole wafer in one final product.

You also need to worry about yields, Apple, AMD etc can sell ”bad” chips as lower core versions, if you’re depending on whole wafer you have little room for error.