The Quran says warners were sent to all nations yet there's not a hint they ever existed.And they swore by Allah their strongest oath that if a warner came to them, they would be more guided than any of the previous nations. But when a warner came to them , it did not increase them except in aversion
An all knowing God wouldn't send failures, he would choose people who could and with his help, would succeed. For them to fail so totally proves your God is either incompetent or he doesn't exist.
And forget Moses, his is a tribal God and he never talks about an afterlife.
As for Christianity, if your God had told Jesus to write down his message it would never have existed, but he didn't.
So all we are left with is the word of one of the many competing self proclaimed prophets. We're not supposed to believe the others so I see no reason to beleive him either.