maybe im just getting old but i cant really understand the runaway success of discord, it seems awfully similar to IRC to me
People were tired of getting DDoS'ed so they switched away from Skype/Teamspeak. The nice UX makes it easy for everyone to use, and the community aspect is appealing. IRC isn't very easy to use for the common person.
A common person can learn. Also the audience (mostly gamers) know how to do stuff with their computers.