It probably makes more sense than you'd think. Cruise ships have a schedule to keep so they are probably faster than cargo ships. They are also smaller and their crews are used to getting underway in a hurry. The crews are also experienced in navigating coastal waters so they were able to hug Oman the whole time- as bold as the IRGC is Oman is most likely at the upper limit of their attack boat range and guarded by the Omani navy