The church helped to bring about the welfare state in two ways. First, the Church embodied the idea of loving self-sacrifice in service of others. “The Word which the Church proclaims demands charity and justice for the poor. As this Word has permeated at least the Western world, an alerted public conscience has demanded public welfare,” write DeKoster and Berghoef. “The Church is the parent of the welfare community.”
But this “welfare community” became secularized when the Church “did not, and perhaps in some respects could not, measure up to her own ideals. Not all the starving were fed, not all of the homeless given shelter, not all of the oppressed and exploited relieved. The cries of the needy ascended to heaven. The Lord answered with the welfare state. The government undertakes to do what the Church demands and then fails to achieve by herself.”
This all sounds pretty plausible, but it’s worth noting a much more direct link between social welfare and Christianity. Determining the origins of the welfare state is a dodgy business, but I think the first recognizably modern social welfare programs (as distinct from, say, the occasional free grain dole) began in Germany following unification under Otto von Bismarck. Political considerations undoubtedly played a role in the creation of national health insurance and a pension system for retirees, but recall that Bismarck famously described these programs as “practical Christianity,” which ought to give you some idea of how such a notoriously conservative statesman could reconcile himself (and the country) to an expansive social safety net.