Portuguese here. This is anecdotal evidence but, as far as I can tell, a lot of our proficiency comes, essentially, to constant exposure to the English language since the early to mid-90s. We don't dub English-speaking media (apart from movies and tv shows more aimed at kids, but even then, Cartoon Network didn't even have subs when I was a kid and I still watched it religiously), the video games we played when we were kids also didn't have a Portuguese language option so we were basically forced to learn English.
And now that the Internet has become widespread throughout the country, the younger generation consume a lot of English-speaking content, so they have little trouble with speaking and writing in it.
This results in a good % of the population having decent to good English, not just the kids but a lot of people in their 30s (and some in their 40s) too.
As a Portuguese who was alive (albeit a kid) in the 90s, I can summarize this as we didn't have enough resources (both human and monetary) to keep enforcing the U.S. drug war model. Since it wasn't working and we were reaching a critical situation (like half of Lisbon in particular was filled with drug addicts shooting heroin up their veins), we turned to the experts.
The article implies this was a decision made from the beginning of this epidemic, but it was pretty much a last resort because the other model was unsustainable for the government. Not sure if we would've adopted it if we had US' resources.
Also, just giving context here, not trying to diminish this accomplishment.