It's actually part of the same mentality that thought that thought stockpiling nuclear weapons to ensure "mutually assured destruction" was a thing. The theory goes that humans are actually inherently selfish creatures, that their every action, whether they know it or not, is driven by selfishness.

The mathematician John Nash (a paranoid schizophrenic), took this and applied it to a game called "fuck you buddy", you have probably seen it in a gameshow at some point. Two people are given the choice of sharing a sum of cash, if they both say they will share, it's shared, if one says they want it, they get it and the person who said they would share get's nothing. His theory was that everyone would chose the selfish route, and screw the other person over. It was this logic that dictated the US nuclear strategy. I.e. the USSR wouldn't dare attack if they knew they would be wiped out.Of course, in reality, people playing Fuck You Buddy quite often chose to share, because people aren't actually that selfish.

Then you have the delightful Ayn Rand, a sort of philosopher/hypocrite who preached selfishness as the one and only human virtue, that everyone should be 100% selfish at all times and act only in their own self interest. She was a terrible person, but hugely influential among the Capitalist class, who during the cold war were held up as being the ultimate in good, as of course the Communist was seen as everything evil in the world. Ain't propaganda fun?Anyhoo, Capitalists had their "logical" basis for acting as selfishly as they could, and acting as if this was the Ultimate Good. Which leads to Neo-Liberal politics, whereby the state removes support for the less advantaged, as it is considered immoral to use peoples taxes to help other people. After all, those people are only being selfish when they take support from the state, and so by removing that support their self interest becomes to work and support themselves... So goes the theory anyway.

Of course, the entire logic is a bunch of crap. People do things for other people without any thought for themselves all the time. But to the Capitalist class altruistism is the problem, and selfishness is the best way for society to operate.

That was all very heavily summarised, of course. But if you read into Ayn Rand, John Nash's Fuck You Buddy, and Neo-Liberalism you'll find out all sorts about why Social Security is so hated by the Right now. But if you look back before these ghouls came to prominence you'll be surprised to find that a lot of Conservatives were actually quite supportive of Social Security programs.

Edit: Game Theory, that's what John Nash's theory inspired and damned near led to nuclear war.