Globalization largely did that but neoliberalism was the driving ideology of the era. Not every city is the same by any means but there was a time when imported products were more expensive due to protectionism. Protectionism is mostly bad for economies so there was plenty of reason to have free trade agreements. But it also meant that in the developed world, a lot of factories moved to cheaper countries and those products were then exported everywhere.

So, it was more efficient. A lot of products got cheaper and became available to people for the first time. But it also meant a place like Manhattan started to feel like the downtown of every global city. Local businesses found it harder to compete to with multinational companies with global supply chains and local stores got replaced by huge chain stores.

It also meant many places that used to have manufacturing became rust belts. Essentially, products and money could move across borders freely but workers could not (and still can’t). So, manufacturers moved plants to places where labor was cheap and/or workers had fewer rights. Unions in America severely declined. Prices also fell — in some cases by a huge amount — so for most people, it was worth it. But a lot of cities (and people in them) never recovered.

When free trade agreements are being passed, the argument in favor is usually that we’ll all be better off. But the economic theory arguing that is basically that we all can be better off if the winners from the change are basically taxed to compensate the losers. Not necessarily forever or with cash transfers but enough that there’s an easy transition. But that requires more left wing policies and neoliberalism rejected that. Bill Clinton’s whole thing was being a centrist who moved Democrats to the right (in response to Democrats losing elections in the 80’s, to be clear, but it still happened). So, instead, people in globalized industries usually just lost their jobs and were largely left to fend for themselves. People were told to “learn to code” so often without any help to do so that it’s become a meme anytime someone loses a job to say “learn to code” sarcastically.

To reiterate: free trade agreements make most people better off. If you didn’t work in a factory that moved, you got cheaper stuff. Lots of people got super rich and lots more people worked for expanding companies or in newly in-demand fields and did fine. But the downsides were real and largely dismissed and ignored by neoliberals for ideological reasons. (and most conservatives, obviously, but they were never advocates of workers the way left wing parties usually are).