Amazon hasn't been just a retail company in a very long time. It is probably THE Tech company at this point. They are a consumer electronics company having cornered the market on the cheap android tablet, and the smart speaker. They are a dominant enterprise cloud player. They own the biggest player in e-sports currently with twitch. They are in the music and video streaming business. They do government contracting at this point. The valuation is more than justified.
And twitch is becoming much more than esports. With YouTube shooting itself in the foot with their copyright nonsense, there are lots of big YouTubers carefully transitioning their content and user base to twitch.
It will come to nothing once Twitch becomes a big enough target. Then they’ll start to resemble YouTube more and more until the in turn are “disrupted.”