He does not tackle the questions: What caused the social contract to exist (primarily in the West) in the first place? And why has it declined?
The best book to provide information on the basis of which these questions can be answered is: Vishal Mangalwadi’s The Book That Made Your World: How the Bible Created the Soul of Western Civilisation
Though Mangalwadi does not go on to cover Mahbubani’s specific points, I think he would say that as the Bible has been rejected in Western society, so the social contract has declined.
My view is that the social contract has existed in various societies and at various times, often as a direct or indirect result of the influence of the Bible, but sometimes also as a result of nationalism, Marxism, tribalism, and so on.
However, it is true that the longest-lasting and most-durable social contract existed as a result of the influence of the Bible, and it is doubtful if the modern world can recover the social contract on any basis other than that provided by the Bible. Individuals can be more or less socially responsible, on any and all sorts of bases. But society needs more than a few whimsical individuals if there is to be a social contract of any sort.
Of course, Mahbubani does not address the question of WHAT SORT of social contract. Traditional Indian society had the social contract of the caste system. Traditional Chinese society had the social contract of Confucianism. Traditional Japanese society had the social contract of Shintoism. Traditional African society had the social contract of tribalism. And so on. But of course Mahbubani is not referring to these sorts of social contract. He is referring, I am pretty sure, to the sort of “modern social contract” by which free individuals in free societies voluntarily took responsibility for society – something that started only with the influence of the Bible from the sixteenth century with Luther, Calvin, and the Radical Reformers – and the influence of the “modern social contract” has declined with the decline of the influence of the Bible. Specifically, the decline of the influence on the Bible in Protestantism (Roman Catholics and Eastern Orthodox have been the majority of Christians since the Emperor Constantine transformed the persecuted followers of Jesus the Lord into state-protected Christianity at the cost of reducing the influence of Biblical teaching).
I should also point out that Mahbubani’s dates are a bit wrong. The social contract was not “of the last three decades”; rather, it was decimated in the last three decades.