https://opensignal.com/reports/2016/08/global-state-of-the-m...
Many "developing" countries never even deployed 2G and dial-up to any great extent. They were simply too poor to build large-scale telephone network infrastructure. When they did start getting connectivity in the late 1990s and 2000s, they were able to skip straight to the latest generation of technology.
This is a pattern we see all over the world — the wealth advantage of "developed" nations is offset by their historical investment in infrastructure that is no longer state-of-the-art.
For example, the London Underground has been in operation for over a hundred years. The newest bits are great, but the oldest parts are hamstrung by design decisions made in the Victorian era. Whereas, when China builds a new metro, it's able to build every part of it to modern standards, applying the accumulated knowledge from building those earlier metros.