Documented cause
Mixer started as Beam in 2016, a gaming streaming startup founded by Matthew Salsamendi and James Boehm, which Microsoft acquired for approximately $100 million that same year. Microsoft rebranded the service as Mixer in 2017 and positioned it as a premium alternative to Twitch with lower latency (near-real-time streaming) and interactive features that let viewers participate in streams. The technical differentiation was real but not sufficient to dislodge Twitch's enormous network effect and creator ecosystem.
In August 2019, Microsoft announced that Tyler "Ninja" Blevins — the world's most followed gaming streamer — would move exclusively to Mixer under a reported deal worth $20-30 million or more. Weeks later, Michael "Shroud" Grzesiek followed in a separate exclusive deal. Together, these were the two most viewed streamers on Twitch, and Microsoft hoped their migration would trigger a mass exodus from Twitch to Mixer.
It didn't. Ninja's audience on Twitch had been built over years through community relationships. His Mixer channel attracted viewers who specifically followed him, but it didn't create the "I want to stream and watch streams on Mixer as my platform" loyalty needed for a thriving ecosystem. Other streamers didn't follow Ninja and Shroud to Mixer — the platform remained small. Microsoft's interactive features didn't compensate for Twitch's decade of community building. In July 2020 — just 18 months after the Ninja deal — Microsoft announced Mixer was shutting down, partnering instead with Facebook Gaming. Ninja, Shroud, and other exclusive streamers received their full contract payouts and quickly returned to Twitch and YouTube.