Real time chat was always present and popular, and there were solutions with the feature sets of Discord. Discord just happened to come at the time when the most popular software (Skype, TeamSpeak) were either bloated or getting thrown into the gutter. So add the GAYMUHR marketing and guerilla tactics (they reward you for shilling and they paid streamers and el YouTubers to kickstart it), some angel investors from Ching Chong Nowhere, the "minimalistic" design, friendly GUI and links/temporary accounts, and you got the rest of the common Internet world by storm, lauding it as something new.
Discord is the new craze for sysops and communities because there's simply no barrier to entry
. Anyone can click on the Discord link on their browser, pick a username and start chatting. The same went for some IRC networks/web clients, but you could only chat, rarely was there any hotlinking support for displaying images or anything else to make it fancier. And the Discord interface is so compliant towards big button syndrome and "minimalist" that people automatically find it appealing. This means higher numbers. People like higher numbers, myself included, it's something natural. Modern internet denizens don't have the will nor attention span to search this spooky IRC thing that only 1337hax0rz (https://www.youtube.com/watch?v=O2rGTXHvPCQ
) use, even though its functional, keeps the bloat out and does exactly what it says in the back of the box.
Imageboards are rooted with IRC culture and chatrooms so thankfully, the transition hasn't been instant. Some *chans have
made the switch, and I have heard of infamous Discord raid groups (so anonymoose we r legion) that go on spamming rampages under mobile networks so they can try to shove their opinions to 名無し on the Four Leaf. A thing that's awfully too common are for Discord links to be posted alongside generals or niche communities and have it overtake/fragment the original site. Discord is like reddit, it homogenizes communities. Why go to that forum when you have a subreddit? Add the low barrier to entry, the demographic brewed from the advertising and the epic humor, creating invites being ridiculously easy, free of charge and everyone and their grandma using it, and you have a fire just waiting to happen outside the garden. And the botnet aspects are ever so worrying too, who knows what Discord can do knowing what porn you watch?
I think IRC does still have some life left to it, and there might be a surge in activity and popularity with the recent late 90s / early 00s nostalgia bubble that's just waiting to burst, so you might see a lot of hippies or 13 year old hax0rz who were born in the wrong generation using it soon. And Discord's userbase might implode due to the botnet, invasive bloat, shitty admin tools, needing bots to do anything, and for imageboards, the many dramas caused by stuck up people on Discord and the userbase it attracts. Not that IRC didn't have its fair share of tripfag wars or drama, but at least not just any
person could join it.