Big GPUs, and we know Intel 10nm yields took a long time to dial in. TSMCs more mature node makes more sense from that perspective alone.
And I agree, the potential for a complete market failure is not unknown to Intel. Having this built on someone else's fab means they lose a lot less if it completely fails to gain any market traction. Which this first round may have a lot of trouble with.
Unless they get the drivers right this could all be a waste of time.
Though like what AMD seems to be planning, slapping one of those dies into a true Intel APU would not be beyond them (heck they might have that in mind, Intel has used Vega once and it was pretty decent) Intel 8+4 + 128 EU, that would be something else.