In part it's a Biblical thing. The Israelite society was prefeudalistic, but a strong dose of scriptural socialism creeps in when the manna arrives to save the wandering Israelites, and God through Moses orders that "you shall take an omer apiece" they gathered some more, some less. But he that gathered much had nothing over, and he that gathered little had no lack." No two ways about it, the Biblical God was -- or those who wrote the texts were -- not opposed on principle to classic redistribution of the wealth by the ruling authorities.
But for Christians it's the Gospels that really count. And Jesus was no free marketeer. Improving one's earthly financial circumstances was not nearly as critical for the Jesus character as was preparing for the end times that he predicted would arrive in during the lives of those who witnessed him. According to the gospels he did offer substantial encouragement for the poor, and warned the wealthy that they are in grave danger of blowing their prospects of reaching paradise, as per the metaphor of a rich person entering heaven being as difficult as a camel passing through the eye of the needle (a narrow passageway through a town or city wall designed to hinder intruders). This caution makes sense, sociological research is confirming that the more securely prosperous individuals and societies are the more likely they are to lose the faith (http://www.epjournal.net/filestore/EP07398441_c.pdf). A basic point of core Christian (and Islamic) doctrine is that the wealthy have at best no more access to heaven than anyone else, offering hope to the impoverished masses who were rejected by other cults that courted the elites. It's a core reason why ChristoIslam is so popular.
To understand just how uncapitalist Christianity can be we turn to the first chapter after the gospel of Jesus, Acts, which describes the nature of the early church. Sections 2 and 4 state that all "the believers were together and had everything in common. Selling their possessions and goods, they gave to anyone as he had need" No one claimed that any of his possessions was his own, but they shared everything they had". There were no needy persons among them. From time to time those who owned lands or houses sold them, brought the money from the sales and put it at the apostles feet, and it was distributed to anyone as he had need."
Now folks, that's an outright redistributory, egalitarian socialist commune of the type described millennia later by Marx -- who likely got the general idea from the gospels. In 2 Corinthians Paul reinforces the socialist ideal, "For I do not mean that others should be eased and you burdened; but by an equality, that now as this time your abundance may supply their lack, that their abundance may supply their lack, that their abundance also may supply your lack -- that there may be equality." Paul then refers back to the Exodus example as a precedent. To appreciate how big a deal this all is consider that the Bible contains the first descriptions of socialism in history. There was nothing socialist about the Roman Empire, or other ancient civilizations. Apparently no one had previously thought up the idea, radical as it was in a prefeudal world. Richards, French and Sekulow attempt to evade the outstanding socialism of their Good Book by pointing out that the Christocollectivism was not governmental, but NGOs can practice full blown socialism. Nor do Richards and company mention that in Marxist Communist theory the state is supposed to wither away leaving no government to enforce the voluntary socialist utopia. Sound familiar?
Frightening passages in Acts further emphasize how not antisocialist the New Testament deity is. And how dark the Biblical Christosocialist cult was. Section 5 details how when a church member fails to turn over all his property to the church "he fell down and died," when his wife later did the same "she fell down" and died" Great fear seized the whole church and all who heard about these events." The theocon gang of three tries to get around this one by explaining that those holding back their property were actually punished for the sin of lying. But that is not all that different from communist enforcers going after cheaters of the collective, and the fear factor language makes it clear that the deaths were also intended to compel compliance through a degree of terror imposed by a God who thinks that those who have joined the Jesus movement but fail to fully embrace the collective are worthy of death. This is a particularly grave issue. The Bible exhibits a perturbing propensity for resorting to lethal termination as a means of imposing conformity, and its ancient writers could not help contaminating socialism with a thuggish death factor from the get-go.
Richards, French and Sekulow go on to contend that the socialism of Acts was but a temporary expedient. Yet the lines in Acts 2 and 4, and in Corinthians by Paul, have the air of a profound Christian ideal of the flock of the Son of God ensuring the well being of its own members (see footnote). An ideal important enough to require whacking off some who fail to fall in line. Most likely Christocommunism soon went a glimmering because it did not work out that well. That Paul later became a social Darwinist demanding that if "a man will not work, he shall not eat" is not particularly good for the faith -- it indicates that the Christian message is not sufficiently powerful and inspirational to motivate followers to work hard simply for the godly goodness of hard work, instead the early Christians leaders had to fall back upon the run of the mill motivators of fear of poverty and the lure of earthly rewards secular elements often rely upon.
Not only are the Gospels' socialist friendly, they are not at all pro-libertarian. It's not hard to figure that one out -- we all know that Jesus said to "render unto Caesar the things which are Caeser's." No libertarian would say something like that, it being in accord with exactly what this country is not about, taxation without representation. It is not an accident that many of the founders, Jefferson, Franklin, Washington, Paine, were Deists who rejected the Biblical concept of rule through Divine Right. Otherwise they could not have revolted against the Crown in favor of democratic free markets that are not described in the scriptures, that not being surprising because capitalism had not yet been invented (while the pagan Greco-Roman experiments with democracy were ignored).
Far from being the antithesis of modern Communism, the system in Acts is accurately labeled Christocommunism. Although not identical to the Marxist-Leninist variety, it is too lethally close. So not only is the idea of socialism a Christian invention, its extreme communistic variant is too. That means that the combined claims by many on the Christian right that Christ hates socialism it being a modern lefty atheist concept is a extraordinarily successful Big Lie that that right wing nationalist socialist, Goebbels, would be proud of -- which reemphasizes the point that nondemocratic collectivism has never been a concept limited to the left.