Agree with all of this. The ridership might be there but I doubt the business case is - and this is true in Europe as well. As far as I can tell sleeper services generally are not money-makers, and are subsidized by regular passenger service.

Which may be a desirable policy outcome for state rail agencies - but this is a private venture!

I think cost is an under-appreciated aspect of this. You're carrying 5-10x fewer passengers per-train, at greater cost (the cost of turning over a stateroom is many times higher than cleaning a coach seat, along with linens, food, etc.), on very expensive custom equipment that isn't suitable for other uses.

There seem to be two "major" (really heavy scare quotes here) players in the US private sleeper service scene. Dreamstar IMO is the more promising of the two (heavy caveat that this is relative to each other, not absolute odds) by realizing the only way to make the economics work is the ability to charge $$$$$ for tickets.

The other (Lunatrain) IMO is just out to lunch, with a claimed focus on affordability. None of the above leads to affordable tickets.