We did not ask for an explanation as to why our seats were given to a more important customer. That would have further distracted us from enjoying our time together and our bottle of Italian wine ;-). Reservation Systems normally perform as intended, until someone manually intervenes, and bumping us in favor of a more important customer is definitely what Celebrity did. For that, our only recourse is to use social media to let others know that they should consider alternatives to Celebrity.
Yes, Celebrity is a for-profit business, as is American Airlines (AA). Even though I quickly requalify for Executive Platinum (EP) status each year, it is very unlikely that AA would treat a "low/no status customer" the way Celebrity treated us. The airline industry business model is to overbook, as most travelers know, but when needed they can quickly find an available seat on another flight even if it means flying on it's competitor. The exception to this is weather, not an issue in Flam that day.
The sales clerk at the ticket office in Flam confirmed to us that Celebrity did not release any of their tickets that day, nor were there any mechanical issues that reduced the Flam Railways capacity that day.
BTW, we booked this cruise on AA's cruise site, and my review of Celebrity's actions are posted on their site, hoping to steer fellow AA customers away from Celebrity and Royal Caribbean Group (RCG). Afterall, it is RCG's Terms & Conditions that one must agree to when booking an excursion. They can cancel excursions the night before docking in Flam, but customers are left with no way to recover from Celebrity's poor business decision.