Pele is fantastic, no question there, but in what world was Pele popularizing the already worlds most popular sport? Maybe this is just a super US-centric viewpoint I'm unaware of as an Englishman?

Yes, definitely US centric but still…

He popularized it a bit in the United States in the 1970’s when he came here to play.

They even put him in the movies, playing soccer/football, of course:

https://m.imdb.com/title/tt0083284/

Great question. If you were an American kid growing up in the US in the 1970's and '80's, football was considered an exotic import (unlike American college and NFL "football"). Youth leagues were a completely brand new thing, underfunded, and not that popular. It was even less popular as a sport among adults at the time, so very little advertising dollars Stateside. The big three in the US are baseball, NFL football, and basketball, with hockey coming in second. Soccer is still playing catch-up in the States. It's still nowhere near as popular as it is in Europe or South America.

I can remember putting on our Adidas jerseys and shin guards and boots (or maybe Sambas), and practicing "soccer skills" in my yard and people would actually stop on the street and ask "what game are you playing?" (I date myself here).

Things are a lot better today, of course, with a dramatic increase in youth leagues and FIFA and Premier League viewership.

he had radio combined with black & white television which were critical media formats coming together and massively popular that contributed

I would say he made the Brazilian team image the stuff of legends. This foot-ball thing was plenty-plenty popular throughout the world, having spread like wildfire throughout the twentieth century.