If you use or like the meme, it is of course obvious to you where it came from and what it means.
The rest of the world that doesn't watch NASCAR or obsessively follow right-wing media (i.e., most of the world) will not necessarily intuit how one is supposed to get "f-word Joe Biden" out of "let's go Brandon"; so the article does a service by providing that context.
Ordinarily the alt-right meme-of-the-month doesn't merit an AP article; but since high-ranking national Republican leaders have begun using this one, it is causing some confusion among people who aren't aware of its origin.