It makes sense to be upset, losing a job is never easy. And it sucks several people were laid off.
But the original content wasn't working and they have stated they are planning on taking mixer in another direction, so sadly the plan to lay off the employee's made sense. Mixer had literally failed to gain traction and gain fans, and again, the point is to grow the platform. It really sounds like Microsoft is going away from the original programming, so it wouldn't make sense to keep those teams and employees.
This appears to be a strategy shift for Microsoft, as Mixer continues to move toward taking a bigger bite of the streaming pie. Cutting whole teams of original content producers indicates that Microsoft is taking a different approach moving forward, potentially tapping its vast network of streamers and influencers that would likely be eager to "step up."
Last year, Microsoft introduced the ability to broadcast everything that happens on their screen through Mixer, specifically for Xbox One. This means when streaming, Xbox One users can show off everything on their interface.
Microsoft fleshed out Mixer with interestingly tools, but the platform has struggled to gain traction. Whether this is Microsoft once again failing to properly push a product or simply the weight of market leader Switch being too much remains to be seen.
Amazon-owned Twitch is certainly the favored choice for streamers. Fortnite is the latest gaming giant and Twitch viewership on the game is around 6x higher than Mixer.
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I've seen people say how Ninja is just a streamer, but he's done more in one week to get people 1.) talking about mixer 2.) downloading the app 3.) making an account than anything previously Microsoft has done. Maybe in a week he'll be down to 10K viewers or less, but so far he's done the job Microsoft has wanted him to. And I don't think his contract is limited to JUST streaming video games. Like others have said, it's probably a multi-year contract with commentary/streaming various events, like the upcoming Halo Infinite showing (whenever that is). They are basically paying for marketing upfront for a video game influencer, that will help visilbility of multiple services, from Mixer to xCloud to first party games.