Here is what the author's main point, he stated:
"However, both Muslims and Christians agree that Moses and
Aaron were sent to Israel and to the Egyptians with their message.
The Qur'an summarizes the section 25:35-39 in ayah 39 with the statement that all those mentioned were completely
destroyed.
But neither Israel nor the people of Egypt were completely destroyed. It seems the writer
of the Qur'an got carried a way with his doomsday warnings and made this point by far too
strong when we look at history and to the people of Israel and the Egyptians. They have
continued to exist from the time of Moses to this day. The Egyptians were not utterly
destroyed."
Let us look at Noble Verses 25:35-39 "(Before this,) We sent Moses The Book, and appointed his brother Aaron with him as minister; and We command: "Go ye both, to the people who have rejected our Signs:" And those (people) We destroyed with utter destruction. And the people of Noah,- when they rejected the apostles, We drowned them, and We made them as a Sign for mankind; and We have prepared for (all) wrong-doers a grievous Penalty;- As also 'Ad and Thamud, and the Companions of the Rass, and many a generation between them. To each one We set forth Parables and examples; and each one We broke to utter annihilation (for their sins)."
The people whom Allah Almighty had destroyed with utter destruction from the Egyptians are Pharoah and his followers from the bad only. We all know that Egyptians still exist today. You did not have to mention that. Allah Almighty did not drown all of the Egyptians. He only led astray Pharoah and the bad from the Egyptians and made them chase Moses peace be upon him and his followers from the Jews and then drowned them all.
Read Noble Verse 10:87 "We inspired Moses and his brother with this Message: "Provide dwellings for your people in Egypt, make your dwellings into places of worship, and establish regular prayers: and give glad tidings to those who believe (from the Egyptians)!"
Noble Verse 10:87 clearly proves that there are people from the Egyptians who believed in Moses's message.