They are random. Not everyone gets these offers, also there are limited amount of offers , once they are snatched up they are gone.
Rule of thumb I always follow, if I see anything travel related Airline, Cruise, Hotel. I will add it to my card ASAP , regardless if I will use it or not. By doing this I notice I see multiple Cruise line offers.
Example here back in Aug/Sept/Oct 2023 I had the following offers, which I had added all of the to my card. I will probably never sail Regent or Oceania due to price. But everything else probably.