As to why they decided not to use you, I cannot say. I have made the mistake in interviews before of being overly confident, and especially of making too many jokes which for some interviewers comes of as sounding irreverent of the seriousness of the job. Try thinking back to the conversation and any awkward moments. That is probably it.
Or there is a very good chance there were 50 people up for the job and someone even more qualified is available to them. For example, they probably hire a lot of Steiner people, because those people already know the life and they know they want the job. Did you makes any jokes or veiled complaints about the living conditions, etc?
Unfortunately, in this day and age is very hard to an answer as to "why" you were rejected, because once they give you a reason a person feels compelled to dispute it - and if they don't want you that just becomes burdensome. Being a "nuisance" in the cruise industry is reason enough not to get the job. Bosses don't like "complainers" or needy people.
I would try Steiners, do the interview in a more professional manner, and see if you get the job (though as far as I know they mostly hire ladies as masseuses).
Then try Harding Brothers again in a year. Do the interview differently, and see what happens. Remember, there are a lot more factors to getting the job than experience. A lot of it has to do with "personality" and such.
Good luck and sorry it didn't work out.