Why Yahweh? (Or Allah, or Zeus, etc.)

[John V]

One can be a spokesperson for God without these claims. Indeed, the prophets and apostles were all spokepersons, but none made this claim.

Another example:
Matt 16
15 “But what about you?” he asked. “Who do you say I am?”
16 Simon Peter answered, “You are the Messiah, the Son of the living God.”

And how does that make him divine?

Claiming to be the messiah (and before you nitpick, Jesus goes on to tell Peter he is correct in his assessment in the passage above) is itself a claim of divinity. Consider this passage from Isaiah 9:

6For to us a child is born,
to us a son is given,
and the government will be on his shoulders.
And he will be called
Wonderful Counselor, Mighty God,
Everlasting Father, Prince of Peace.
7 Of the greatness of his government and peace
there will be no end.
He will reign on David’s throne
and over his kingdom,
establishing and upholding it
with justice and righteousness
from that time on and forever.

Mighty God and Everlasting Father clearly indicate divinity. Jewish scholars before and after Jesus considered the above verse to be messianic.