Because they operate under the cover of a religion. Persistence after death is fundamental to religion and nowhere is it found in Judaism. Their resurrection is earthly.
Apollonius of Tyana said, "You see how the sparrows care for one another and delight in communism, but we are far from approving of it, nay, should we happen to see anyone sharing his own in common with others, we set him down as a spendthrift and talk about his extravagance and so forth, while as for those who are supported by him, we call them parasites and flatterers."
The key to Israel's success is instinct. The problem is, they only care for their own kinsmen...
I don't doubt that apostle Paul sincerely wanted to help his own people out. But to achieve this, he had to compromise truth with lie and bring two opposites together: Jesus' all-pervading deity with a tribalist god of wrath, with little regard for Gentile proselytes.