Jobs delaying treatment likely made it worse for him, but I don’t think it’s fair to say his disease was curable. Especially when compared to something like melanoma that’s 90% for five year survival [1].
Had his fruitarian tendencies led to him dying of hepatitis or something, that’s a different story.
[0] https://www.hopkinsmedicine.org/health/conditions-and-diseas... [1] https://www.cancer.org/cancer/melanoma-skin-cancer/detection...