Question

Read the passage below:

In May 1939, self-taught archaeologist Basil Brown began excavating a large earthen mound, known as Mound 1, on the private estate of Edith Pretty in Sutton Hoo, Suffolk. Pretty had commissioned the dig after observing mysterious ridges across her property. Working under the auspices of the Ipswich Museum, Brown initially uncovered iron rivets spaced symmetrically along the soil, leading him to conclude that a wooden vessel had been buried there centuries earlier. By July, as the full outline of a ninety-foot Anglo-Saxon ship emerged from the sand, professional archaeologists from the Ministry of Works, led by Charles Phillips, assumed direction of the site due to the national significance of the find. Inside what had been the central burial chamber, excavators discovered an extraordinary array of gold ornaments, silver feasting vessels, and a famed ceremonial iron helmet. Crucially, the absence of human skeletal remains prompted intense scholarly debate. Soil testing later revealed that the highly acidic soil of East Anglia had completely dissolved the organic matter of the deceased king, likely Raedwald of East Anglia, who died around 624 CE. To preserve the delicate impression of the ship's timbers, which had turned into dark staining in the sandy soil, Brown used soft plaster casts and photographed every layer prior to removal. The artifacts were donated to the British Museum by Edith Pretty in August 1939, shortly before the outbreak of World War II, ensuring their safety in underground railway vaults throughout the conflict.

According to the passage, what was the reason no human skeletal remains were found in the burial chamber of Mound 1?