Forgive my nerdy rant below
But....
It was a big deal because of its positive portrayal of an African people and culture. Most of its money actually came from the North American box office (now about $699 million) because besides the usual demographic for CBMs/Superhero movies, black Americans made it a cultural event. Celebs bought tickets for entire schools and neighbourhoods to make sure black kids saw it.
It was just brilliant marketing by Marvel to highlight the fact that it was the first Afro-centric movie of its kind and scale. And they had been doing so for a year before release. No one had ever put $200 million into a black-centred movie with an almost entirely black cast before. So Disney/Marvel kinda took a risk there with Black Panther, but it paid off. I think they did it to compete with Wonder Woman after WB/DC announced they'd make it.
The "international" box office for BP did ok and was normal for such movies when they do well: it's about $647 million now. Normally, such movies do about a 35/65 % split between 'Domestic' (North American) and foreign (International/outside NAmerica), so a 'normal' box office performance for Black Panther sans the cultural effect would've been something like $300/650 million performance, so it should've performed in the 800 to 900 million range world wide if it had not become a cultural phenomenon. Maybe closer to the 800 because it was a bit of a cultural phenomenon in other places in Europe, SA and Brazil where you have significant numbers of Black people as well. For example, Wonder Woman made about $820 million and was considered wildly successful (though its budget was half of BP's).
Only ensemble CBMs do as well as BP did. The 3 Avengers and Cap America: Civil War (which is, truthfully speaking just an Avengers movie) are the only ones that make much more than $1 billion in the genre. Iron Man 3 was the third instalment and part of an already large universe before it did a lil over $1.2 billion and was before BP the top grossing solo superhero film. It's truly crazy how well BP did. A phenomenon. $1.343 billion and counting!!!! God damn.
But I guess you have to be in some way into that genre to enjoy it. It was technically a continuation of Civil War where BP was first introduced, itself an instalment of a long series of movies in the MCU universe (with now about 19 movies). If you are not into CBMs and haven't been following the MCU since the first Iron Man a decade ago, I guess its success looks weird. But if you compare it to other movies in the MCU, it's a well-made film. However, when you leave that universe and that genre, the success looks crazy for such a film. That's because the genre has a huge dedicated fanbase. Like Star Wars. Actually, MCU now rivals Star Wars as the most successful franchise if you don't factor in average returns per movie. If you do, Star Wars is still first. But not for long. With the next 4/5 MCU films planned for release in the next year and a half, its gonna tko Star Wars. Already Infinity War is on pace to make 2 billion!
(It's at 1.9 billion in less than a month!)