I think the bottom line on the Grand Luxe and other 'cruise trains' that have been tried is that those for whom price is no object (the true 'market' for GLE) either don't consider ANY train to be worth a luxury price, or, a train is just not one of the options they would consider for a short vacation or cruise (the destination is more important the how they get there). While there those of us that may take a once-in-a-lifetime ride such as this, there aren't enough willing to do so to pay the bills. Apparently, the only 'cruise trains' that have more than a 2-3 year life span are the Orient Express and the Blue Train. And even the OE was gone for a while before it, too, was revived.
Off the top of my head, I can name at least a dozen dinner trains and a several of 'cruise trains' that have come and gone in only a few years. As I see it, the economics of running the train in addition to all the onboard amenities dictates either a 150% load factor or less than a 'great' experience. It takes a year or longer of 'expectations' of more customers or more trips that are not fulfilled before the management and investors of such endeavors finally decide their projections of business were overly optimistic and costs underestimated. I've done the same in my own business attempts, and therefore only too familiar with the situation.
When considering the GLE, obviously, the 'routine' costs of en-route train servicing, re-stocking of supplies, etc, required a substantial outlay of time and expense even before the first passenger boarded! Like Amtrak trying to pay all the overhead costs based on one train per day on an LD route, GLE running one or two trains per year on a particular route resulted in the overhead costs exceeding the revenue. Regretably, the realization that ends won't meet and hence, no profit, don't sink in quickly enough amid great expectations and much pomp and circumstance.
While I've had the experience of riding the some of the 'great' passenger trains as a kid in the 50s, and even a number of private railcar trips more recently, I've never had the time nor the finances necessary to ride a 'cruise train'. I'm sure, for many, the extent of our rail cruises has been limited to Amtrak, and more so on VIA.
So, it is time to bid adieu to another once-in-a-lifetime trip I wanted to take someday, but that day never came.