You know, making manuscripts, making footage, recording audio, editing it, rendering it properly, publish it and link it all up and make sure it's all good.
There is a lot of work involved that you clearly have no clue about. Working in a team is given to even be able to pump out that much content in such a short timespan.
He's constantly keeping himself updated. He has a dedicated Startcraft 2 channel. He does Let's Play's. He does podcasts, interviews and whatnot here and there. Keeps up with game releases and finding out which one to make a first impression of, look up the developers what they've done and what they are known for and finding general info about the game, especially things people might have criticized it for or praised it for. Replies to two emails very often (I would assume somebody else picks them out for him) through a mailbox video where he also would need to look up shit or at least prepare himself for the question.
It's a fuckload of work.