That's not an excuse to be a douche.
Look at it more as theater than actual reality. Like a scripted drama. Literally pro wrestling status.
Sure, they meant it by stating their points and defending their egos, but they brought their personalities from a 5 to a 10. They went overboard because that's how you promote things.
It's the classic wrestling heel vs. face program, which always draws eyes. That's why everything adapts it. Movies, boxing Muhammad Ali anyone?), football (Richard Sherman anyone? Tom Brady anyone?), TV shows, etc. etc. etc.
Nearly all rivalries to some extent fabricated with the intensity, and it's okay to admit that and still enjoy it. It's called "suspension of disbelief," which is why pro wrestling, science fiction, and fantasy elements are still accepted in modern civilized society. We recognize it is real, but are willing to pretend like it isn't. Think of it like that, but on a scale from 1 to 10 a 2 at the highest, but more likely a 1.
Both of them made a lot of money out of it via Twitch subscriptions, and VGBootCamp likely did as well (if I were GimR, I'd send Leffen a love letter on Valentine's Day, lol). Leffen partially got a sponsor out of it. Both got eyes on them, and the viewership for all of their matches shot up. This match had an insane amount of viewers (again GimR, send Leffen a love letter), and pushed Mango vs. Leffen to peak out at over 116,000 concurrent viewers live as it happened, which was at like 3 in the morning ON THE EAST COAST!!!
Those numbers, that attention, that stuff... that's good for competitive Smash. It brought eyes to not just those matches but other matches as well, and heck, other games. Melee players should be lining up and thanking them for that exposure, because that's gonna get some people some free looks from potential sponsored eSports team. Heck, even Smash Wii U players will benefit from this. Bringing eyes to the product except in the case of scandals is always a good thing. Competitive smash enthusiasts need to think of ways to do this, and Leffen and Chillin found a way by being themselves, all while bringing their personalities and egos up from a 5 to a 10.
If you want competitive Smash to grow, you need stuff that brings eyes to the table. Good feuds, great heels to boo against, great faces to cheer, rivalries, stakes, a reason to care, all those things bring eyes, and all those things were big draws at APEX 2015 and were a reason why everyone benefited from Leffen vs. Chillindude.