I doubt that there was ever any illusion that if financiers could arbitrage labor rates between nations that they would. Hence the expectation always was that living standards among nations would tend to equalize.
Post WW II the US had about 50% of the global GDP. The situation was huge inequality between nations. That was politically untenable and the solution was seen to be development of other nations' economies. Some of this was accomplished with things like the Marshall Plan and some with programs of foreign aid to underdeveloped countries.
However, the US taxpayer would never support a large enough foreign aid budget to really solve the problem. On the other hand, free trade could be sold politically, companies would export capital and know how to lesser developed countries, and the problem of inequality between nations could be ameliorated. Of course, it was at the expense of the US worker whose standard of living stagnated from the '70s onward. But the bet was that other nations would develop slowly enough, US consumers would enjoy cheap goods, business would make lots of money, and that US standard of living wouldn't actually decrease significantly for a politically potent group.
Of course, there aren't enough resources in the world for all 7.5 billion people to enjoy US standard of living. Therefore, the implication of greater equality of standards of living between nations is less equality of standards of living within nations. Less inequality internationally implies greater inequality intra-nationally.
And that is exactly what has happened. The world, including the US, will tend towards the situation in India where there is extreme wealth and extreme poverty side by side.