Well I am an atheist myself, but the key is that in the old testament god gave every human the blame for the original sin.
And the special thing with Jesus dying and taking all sins with him is, that now god won't hate every human just because Adam and Eve stole some fruits.
This some weird story but yeah. Basically after Jesus, god wasn't that angry anymore.
I did mean that.
It was just most noticeable in dolphin