I'm not sure about a recent uptick in fights on cruise ships, I did view the two more recent large fights that took place on Carnival and Royal. I've seen videos of fights going back years ago and on different cruise lines. I believe the two more recent videos are receiving the attention they're receiving due to the size of the fight and the many people involved.
I do agree with you with repercussions, I feel the cruise companies should start making an example and publicly placing these people on "do not cruise" lists in addition to expelling them from the ship at the next port.
In the two viral videos it appears that the security response was slow. I'm not sure if this can be attributed to the crew shortage that the cruise lines are experiencing.