Why? What do these masses of the underclasses see in him that we of the rich and self-sufficient Western uber-class cannot or choose to no longer see? Jesus identified most profoundly with the weak, the poor, the oppressed, the down-trodden, the forgotten, those of no account. He challenged the mighty and powerful of the elites of whatever sort. The oppressed and hopeless and least esteemed are still those that flock to him, just as it was two thousand years ago. And, just as it was two thousand years ago, the rich despise him, mock him, and seek to kill him/get rid of him.
Part of Rome’s genius was adoption and adaptation—the ability to absorb and assimilate all comers, repurposing them to serve Rome’s dominant vision as the great civilizer of the world, the great unifier giving everyone equal access to the same gods and guiding principles. The Emperor was the supreme symbol, the creator and maintainer of this unity—the “Saviour of mankind”, the “Son of God” (Jupiter, Zeus, Amon-Ra, Baal, whichever high deity was relevant to the people in question). Every subject and citizen of the Empire owed their final allegiance to the Emperor as the incarnation of Rome’s “genius”, or “Spirit-Guide”.
Rome incarnated a direct claim by humans to establish an eternal kingdom on earth by right of conquest and coercive power. Local gods could bow and be absorbed into Rome’s in order to survive, or be annihilated like those of the Carthaginians and Druidic Celts. The Jews and Christians challenged Rome’s nature at its root. Both paid a massive price in millions of lives for continuing to seek and honour the true Creator.