Twitch streamers helped Discord gain early users. The connection mattered because Discord launched in 2015 as a low-latency voice, text, and video service aimed largely at gamers, while Twitch already concentrated large gaming communities around live broadcasts.
Discord was created by Jason Citron and Stanislav Vishnevskiy after the failure of their mobile game Fates Forever. They wanted a simpler, less performance-intensive way for players to communicate during games such as Final Fantasy XIV and League of Legends. Relationships with Twitch streamers gave the new service visibility among exactly the audience most likely to need persistent voice channels and community servers.
This does not mean Twitch owned Discord or that Discord was built as a Twitch feature. Twitch was an independent livestreaming platform; Amazon acquired it in 2014. Discord also grew through gaming subreddits, esports communities, and groups devoted to games such as Diablo and World of Warcraft. The broader lesson is that streamers were an important early distribution channel, not the only source of Discord's initial users.