The relevant point isn’t “the realistic world, where the clever scheme fell apart”, the relevant point is “the realistic world, where there is some probability of the clever scheme falling apart, and you need to calculate the expectation of that probability, and that expectation could conceivably go down when you add Godzilla”.
Or to put it another way, even if the worst case is as bad, the average case could still be better. Analyzing the situation in terms of “what if the clever plan fails” is looking only at the worst case.
The relevant point isn’t “the realistic world, where the clever scheme fell apart”, the relevant point is “the realistic world, where there is some probability of the clever scheme falling apart, and you need to calculate the expectation of that probability, and that expectation could conceivably go down when you add Godzilla”.
Or to put it another way, even if the worst case is as bad, the average case could still be better. Analyzing the situation in terms of “what if the clever plan fails” is looking only at the worst case.