The mini pc is not necessary if the TV has the player built in. But they don’t and most people don’t have a second computer in their living room for that purpose. That is why they buy Apple TV or Google chromecast. So these mini PCs will compete in that market.
The player is not the only source of revenue. It is just the easiest to enter and company can start right away. They can also make money from companies that compress video but that will likely happen later when they set up a compression farm. The mini PCs can probably be used for that purpose.
Still a long way to go until the entire business plan goes into action.