Why hades called the god of death?

Answer 1

Hades is MISTAKENLY called the God of Death, when Kronos died his kingdom was split into four parts: The Sky, The Oceans and Seas, The Earth and The Underworld. Zeus, Poseidon and Hades challenged each other for who should rule which part. Zeus won and chose the sky, Poseidon came second and chose the seas, and Hades was left with the Underworld. The earth was then left for the goddesses to tend.

The Underworld is where the living go when they die. Because Hades rules the underworld he is referred to as the God of the Dead, However, in actual fact it is Thanatos who is the God of Death and NOT Hades