Thank you for this analysis. I tend to look at this from a higher level - even if it is LEGALLY responsible for MGM Resorts to launch this lawsuit, it could have wider BUSINESS IMPLICATIONS. (Or it may not; I'm not sure how many Vegas vacationers will use this as a criterion to decide where they will stay.)
"Ultimately the company makes the decision on what the lawyers should do - sue or not."
I agree, but, as you mentioned, this move is entirely based on potential loss of $$.
While the move could face potential backlash and hurt their brand financially, the exposure risk to thousands of lawsuits from victims appears to have been determined to be an even greater financial risk.
I think the main thrust of folks suing MGM is that they let this guy bring suitcase after suitcase into his room and nobody ever questioned it. I'd bet the plaintiff's lawyers will move to have the SAFETY act defense declared irrelevant.