This is another good point! In fact, after campaign 1, the idea that these games have been DMed by a single person has always been an illusion. Brennan specifically pointed it out in an interview prior to this campaign being released, he said something along the lines of “what you see as me DMing this campaign is actually the work of like a dozen people in a me-shaped trenchcoat.” (Not a direct quote, just a half-remembered paraphrase). But his point was, it’s a TV show. There’s an entire team involved in managing all the lore and story threads and logistics behind the scenes, and home DMs should not expect to be able to replicate the work of an entire team of people by themselves.