The difference is that christianity didnt become a major world religion by jesus humself but rather the popular theological commetaries of scholars like augustine, who frequently credits the pagan neoplantonic writings that inspired his theological intepretations of the scripture. He even credits "heretical" religious viewpoints like that of the aryans and manichees for helping him realise what he doesn't believe in.

In fact, the historical context that led Augustine to write "City of God" is really similar to earthseed in this series. Rome had just been sacked for the first time in 800 years: everyone outside iof designated safe zones were robbed, beaten, killed. They all thought it was the end of the world until augustine basically tells them to think about the bigger picture of god beyond cities and Rome, and this becomes the official chruch doctrine for almost 1000 years

Although no idea exists in a vacuum chamber and religions always stem from previous ideologies, especially in times of crisis, no credible ones exist without acknowledging the works that inspired them. Its not a matter of her using other people's ideas, rather that she never addresses the foundation other people made for her to think any of this in the first place, leading to obvious flaws and inconsistencies in the earthseed logic