I don't know, maybe because the exact same Pharaoh that Allah declared to make an example of (after he drowned) was found in water in a terribly preserved state. Case in point Ramesses II.
Maurice Bucaille was the first person who claimed that the Mummy of Ramesses II, is the same one about whom Allah told in Quran that He is going to preserve his dead body.
But what was the proof that Maurice Bucaille provided for this claim?
Maurice Bucaille claimed that the Mummy was full of "SALT", which proves that this Mummy was the same Pharaoh who was drowned in the sea, and thus this "salt" has come from that sea.
But contrary to Maurice Bucaille claim:
(1) The Mummy of Ramesses II didn't come from the Red Sea, but it was taken out from the "Valley of Kings" (where many other Mummys of Pharaohs were buried).
(2) And the "salt" upon the body of Ramesses II, was not from the red sea, but it was a type of salt, which is known as "Natron" and has been extensively used for the purpose of preservation.
Not only Ramesses II, but "all" the Mummys were preserved by using this Natron Salt.
Most Perfect Method of Mummification
https://en.wikipedia.org/wiki/Mummy
The body was further dehydrated by placing it in natron, a naturally occurring salt, for seventy days. Herodotus (the Researcher Scientist) insists that the body did not stay in the natron longer than seventy days. Any shorter time and the body is not completely dehydrated; any longer, and the body is too stiff to move into position for wrapping.
And the body of Ramesses II was not found in red sea, but in the "Valley of Kings".
Ramesses II
https://en.wikipedia.org/wiki/Ramesses_II
Ramesses II was originally buried in the
tomb KV7 in the Valley of the Kings but, because of looting, priests later transferred the body to a holding area, re-wrapped it, and placed it inside the tomb of queen
Inhapy. Seventy-two hours later it was again moved, to the
tomb of the high priest
Pinudjem II. All of this is recorded in hieroglyphics on the linen covering the body.
[58] His mummy is today in
Cairo's
Egyptian Museum.
Moreover, there has not been a single proof that Ramesses II was the same Pharaoh who existed during the era of Moses.
Many WRITINGs have been found from the place of burial of Ramesses II, and they have a lot of details about Ramesses, about buildings, about wars, about progress in Egypt etc. but not a single hint is present there about Moses.
And the name of the wife of Ramesses II was not "ASIYAH" (the wife of Pharoah of the Moses era). But the wife of Ramesses II was a famous queen whose name was "Nefertari".
Therefore, there exists not a single proof that Ramesses II is the same Pharaoh of Moses era and Allah fulfilled any of his promise regarding him, but still propaganda is so strong that millions of people have been decieved in believing this miracle of Quran and thus they accepted Islam due to this lie.