Why did the Egyptians had a book called book of the dead?

Answer 1

Because it has all of the old Egyptian kings of the past written down inside it so that they will never be forgotten

It mainly though, contains spells that they believed would helped the deceased person through the underworld and to the afterlife. The Afterlife is what they believed in most and they wanted the kings to reach there safely

Answer 2

Egyptians were entombed with a collection of religious hymns, magical terms, and moral principles-together called the Book of the dead, Among its moral principles were I did not steel, I did not murder, I did not lie, I have given bread to the hungry and drink to the thirsty.

Answer 3

so it would guide the dead through the jurney of meeting the gods