It’s only my interpretation of it, so be wary. My idea is that after ww2, USA was terrified of USSR, so they did their best to avoid countries “falling” to it.

This best was of two categories: if it was an old power, feed it with all possible money, so they can can develop an industry to get all of the modern commodities (home, car, a fully equipped kitchen…) If it was a colonised or USSR friendly country, forbid all trade, and feed civil war with all means possible, so that this country stop being communist.

Then, democracy had that people had to be listened to a bit, or they would vote communist. Car industries were favoured because it can be converted into a war industry if it needs. Roads and trains are also war assets. Healthcare and food are priorities to make people happy. Education and research are priorities for any country that want to stay relevant, and these benefit from co-operation with other countries.

The way I see it, the west built solid infrastructures and invested in the people in order to fight USSR, while USSR progressively fell into an oppression that prevented these progresses. The third world countries were left alone because no side would allow them to join the other side.

Now the world is full capitalist, so no one will invest in the countries that were left behind. With less investment they progress more slowly.