GMAT Sentence Correction (SC) | Diabetes, together with its serious complications, ranks

The OA says that "only" should be placed after "surpassed", not before, because it limits "by hear disease and cancer", not "surpassed".

..., only surpassed by heart disease and cancer. ---> Wrong
..., surpassed only by heart disease and cancer. ---> Right

Could you please explain this observation in further detail?

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