The last major holdouts in the protest against Reddit’s API pricing relented, abandoning the so-called “John Oliver rules” which only allowed posts featuring the TV host. It's the official end of the battle. The Reddit protest is over, and Reddit won.
Big platforms like Facebook, Digg, Twitter and Reddit don’t fail in a day. Their decline is rather gradual. If you noticed any decline on Reddit’s quality after the API lockdown, then that’s the beginning of a gradual slide. Just wait for a while before judging the results.
My wife didn’t really pay attention to the reddit controversy and frankly didn’t really care. She is about as casual ad you can get and even She has noticed a very steep decline in the quality of content shared on reddit. She barely uses it anymore. Now this is a person who doesn’t notice when her adblocker is on or not. If she noticed this, i can guarantee she is not alone.
It depends on precisely what you mean by “fail” and how strictly you take “day”, but Digg did lose 50% of its traffic within 30 days (and it never recovered).