Why would you connect an AppleTV to an HomePod? It'd be best to spend a bit more and get a decent Home Theatre system. Most likely, you'd get more use out of the HomeTheatre.
To each his own, my friend, to each his own. It depends on what you are trying to accomplish. For example, I've got a TV in my bedroom. I have zero interest in putting a home theatre in my bedroom, but the TV speakers suck so I need something. If I had this it could sit near the bed and broadcast the sound from the TV, which is a good 20 feet away, without the volume being up so loud that it wakes the kids.
Of course that being said, my own complication is that I don't ONLY use the AppleTV in there...I also have a Tivo Mini and the built-in apps on the TV itself (for Netflix and Amazon). currently I have an external bluetooth transmitter sending sound to a Bose Soundlink near the bed...if the HomePod doesn't also do Bluetooth then it would not work in this scenario.