oristarA > "Blowout, "big victory" and "brand new map" - all the three are started with "b": Do you think if it is the alliteration - a rhetorical device being used here?
It's hard to say. You noticed it, so it may have been intentional.
Some writers enjoy the intellectual challenge of alliteration. I've known people who've become very good at doing it on-the-fly. It's a good brain exercise, and encourages the enlargement of one's vocabulary. And it's just fun to do—and for most people, such as we word nerds, fun to hear.