I guess I don't know what you mean by Hellenised and 'child of classical antiquity'. I either wholeheartedly agree or think there's a categorical error (maybe surrounding the definition of Christianity) in your thought.

If I understand it right, Christianity spread fastest among Greek-speaking populations, rather than the Jewish population. From what I understand, the various letters of Paul and the gospels were all written in Greek, rather than Hebrew.

Those facts are true, yes. I wouldn't characterize them as "Hellenisation" and "child of classical antiquity" is all. Koine Greek was the lingua franca at the time. It makes sense that the writing would be more accessible to the Greeks as well.

Why wasn't Christianity more popular among the Jewish people? The Bible has some theological answers to that question. I wouldn't consider a Greek heritage to Christianity to be a main cause of that though. Jesus and the apostles were all Jews, after all.

True, but that wasn't what I meant when I said that the "Greek spawned Christianity". In my mind, the Greek heritage came later, through St Augustine and other philosphers. They relied heavily on Greek philosophy to construct and validate the Christian view of God and the world.