Rawls starts out well in his
Theory of Justice, but where he went astray is the same thing that leads so many leftists/socialists/statists astray: he failed to comprehend that wealth is not a given to be "distributed", but must be created through human action. Give people freedom of action and the incentives that go with it, and lots of wealth will be created; deny freedom, and you are left with poverty. The problem with Rawls's theory is that a society that applied his theory could end up in wreched poverty, but as long as everybody were equally poor, that would be just and OK with him.
According to Rawls's theory, inequalities were just if advantageous to the least advantaged member of society. Yet Rawls was forever blind to the fact that it was far more advantageous to be a semi-poor person in a rich and free but unequal society like America than to be a wretchedly poor person in an "equal" society like Cuba.
"he failed to comprehend that wealth is not a given to be "distributed", but must be created through human action"
His book has a whole chapter on trickle-down, basically. He's rightly accused by leftists as being an apologist for capitalism. Because if you believe in trickle down, then under this difference principle, in theory great inequalities of wealth can be justified.
I don't think it's a meaningful statement to say he failed to understand that wealth is created through human action. That would be true of socialists, whom Rawls directly critiqued. Are you just assuming he believed these things because some uninformed posters above says he does? That's kinda a problem, if you ask me.