Have you ever raised a baby? They're 90% drama, 10% sleep. Guaranteed the early days of the Truman Show were flooded with parents watching the actor mom struggle to deal with the constant crying. Crying because hungry, refusing to eat because they're too busy crying, crying because they're tired, but too busy crying to sleep. I bet tons of parents were watching it, commiserating, or judging, or arguing about how she should be doing this instead of that. The drama writes itself.

Not to mention the moments when they're being extremely cute. When they roll over in bed and stare wide eyed at a stuffed toy, then flail at it and coo little baby noises at it. Maybe bite on it and shake it around like a little puppy. People love that shit. If a live stream of a fixed camera in a car cafe can get millions of views, a live stream of a baby doing baby things can easily get lots of viewers.

Well there can be drama between the characters with the baby as the catalyst for the conflict.

In the early years he would have been barely a prop. Things happen around him but not to him.

You watched Full House season 1, right?

Compare Canonical. Shuttleworth has apparently lost bags of money on his dream, for like decades by now, and apparently only last year or so showed a real profit, but kept on going. Same deal.

Most viewers of the Truman Show would probably just watch clip shows or some influencer explaining what happened that day. I know some people listen to 4 hours of Rogan, but many just hear about him from people reporting on his show.