I think you're assuming the family has seen the video. I don't think so. I mean, would you watch a video KNOWING that, at the end, you're going to see your toddler fall 150(?) feet?
Personally, I would have to watch the video. My husband is way more sensitive than I am and I'm fairly certain he would also feel the need to watch the video.
At the very least, I would expect anyone to have some trusted friend or family member watch the video and tell them
exactly what happened. It was not a graphic or violent video (at least the surveillance footage from inside the cruise ship), so I would need to see exactly how he picked her up, how she was on the railing, whether he let go or whether she forcefully wriggled out of his arms, etc. I do think it was an accident, but as a mother I would need to see with my own eyes exactly how careless or stupid he was to see if it was really a mistake that "could happen to anyone" or if it was completely his fault. That would likely determine my relationship and interactions with him moving forward.
Now it's about whether the cruise line is/was fundamentally negligent in having opening windows through which they should/could reasonably expect people to be falling/dropping babies out of.
I have never been on a cruise ship, but every photo and depiction I have seen throughout my life shows big open expanses of railing that anyone could climb on and potentially fall over. Is that how they are designed? If it's acceptable to have open railings/balconies/etc, then why would open windows be any more negligent on the cruise line's part? I think that's a known danger that you are acknowledging when you choose to board a cruise ship.
Our mall has glass railings and I was always freaking out when my kids got too close and you could see the next level down.
My mother has some mental health issues and is also very afraid of heights so this has also become a big fear to me through many years of conditioning as a child (we couldn't even walk on the side where a railing was). I think most people don't notice because they're not as acutely aware of railings/ledges/etc, but I cannot even begin to count the number of times that I have seen someone plop a baby up on a ledge at a mall, at the zoo, on a boat, at Disney, etc. or let their kids lean/bang on glass where there is a massive drop on the other side.
Every single time I see it, I panic and feel like I'm going to vomit. It was the exact same reaction that I had to the video of this incident. Because every time, in my mind, I envision the same outcome. I knew my mom was a bit over-the-top, but I would have assumed that this was a natural survival instinct that all humans would have to a lesser degree. But, the frequency that I see this type of behavior makes me think that some people must not.