Since those who wrote the Epic of Gilgamesh did not have specific revelation from God, but only the memory of the event as passed down through their culture, they speculated about its meaning and spiritual cause. In their version, a god run amuck tried to wipe out the world but failed. In the Biblical version, the true Creator God was showing mercy by preserving Noah, preserving the seed promise given to Eve, and preserving future hope for the whole world through the promised Messiah. God simultaneously revealed his wrath against all sinners and His mercy toward all people of faith. The issues were clear because God gave special revelation. The pagans, remembering the same event but not having inerrant revelation, could only speculate. They concocted an understanding of the spiritual world by extrapolating from what they saw in nature.
Gilgamesh - Ancient History Encyclopedia
The Greatest Literature of All Time - The Epic of Gilgamesh
No one person wrote The Epic of Gilgamesh