GMAT Sentence Correction (SC) | Re: The nephew of Pliny the Elder wrote the only eyewitness

(A) The nephew of Pliny the Elder wrote the only eyewitness account of the great eruption of Vesuvius in two letters to the historian Tacitus.
(E) In two letters to the historian Tacitus, the nephew of Pliny the Elder wrote the only eyewitness account of the great eruption of Vesuvius

I still don't get the difference between these 2 choices: (A) it was said that "in two letters to the historian Tacitus" could modify great erution of Vesuvius --> but in (E) In two letters to the historian
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