The video doesn't make that assumption. It has relatively straightforward calculations about the size of the market, the existing competitors, the number of satellites needed to support a customer base of whatever size given SpaceX's own numbers. And the economics don't make much if any sense. The only objection I had is that low latency internet is more useful than just to gamers. E.g. voip and video calls, even ordinary browsing are unbearable with high latency connections.