I've lived in Florida for most of my life.
When Disney World was built, alligators were receiving protection from the Lacey act and later would receive additional protection by being declared endangered just a couple of years later.
This poor two year old boy was the very first victim for the year in all of the state of Florida. Last year, only one person was fatally attacked. That person was killed in a spring that had always been safe for swimming up in an area of the spring where I had never seen a gator. This spring had/has excellent visibility. But, we get complacent swimming in an area that has always been safe. The person who was killed had gone diving in that same location many times.
Disney has significantly less gators than it would if it wasn't managing gators proactively. There is a trail near my home where I routinely walk and on a 2 mile walk I can EASILY count 40 gators sunning on the banks of what is little more than a marshy drainage ditch. I've only seen a few gators at Disney and I've been there quite a bit. If Disney wasn't managing gators, you would be able to count tons of them on the banks. Of course, those you see on the bank are only some of the gators that are actually there.
Additionally, the gator involved was of a size that is usually still very skittish. I spook 7 foot gators on a pretty regular basis. They usually have to be bigger than that to be bold enough to be a problem. 6 foot and smaller usually dive into the water and swim away when I'm within 20 feet or so. The big ones stay on land and watch you.
We all decide what risks we will take. I don't let my daughter wade in or play near freshwater bodies of water here in Florida even though she is a LOT more likely to die in a car accident on the way home from the park. I had good friends growing up that swam in the water on a regular basis without mishaps despite the large gators.
Pretty much, what happened to this kid was nobody's fault. It was a fantastically rare freak incident.
One of my favorite trails was ruined by tourists in the last few years. This is a trail that has tons of gators, but, also great migrating bird viewing. Anyways, despite tons of warning signs, tourists kept approaching and trying to handle baby gators. The park tried to keep it under control by posting a ranger, but, people kept approaching gators. They finally built a raised platform with a locked gate at the end and now the trail is a few hundred feet long instead of 2 miles long. From what I understand, now they only open the rest of the trail when they have the staffing to post what are essentially babysitters for tourists.
But, even with hundreds of ignorant people approaching tons of gators and attempting to catch baby gators, somehow, NO ONE GOT KILLED.
I share this point to illustrate how truly rare it is for a gator to actually kill a human.
There is a marina and dock near my home where people fish off the banks of a river which is just full of gators. On weekends, even small children are fishing right at the water's edge. That is a scene repeated all over the state of Florida and yet this poor kid is the ONLY gator fatality.
It's just bad luck.
If we're being truly honest with ourselves, the reason this is so upsetting is because it illustrates just one more way in which we are not in control. It's just one more thing to be afraid of. I think that people have really latched on to it because no one wants to think about Pulse nightclub and what might have happened at Disney. Which could really happen anywhere. But, that's not something we can control. We can control whether or not we go near freshwater in Florida. Alligators seem like a less complex problem and it's easy to get caught up in the 'put up a fence' 'post a better sign' rhetoric. You are still statistically more likely to die in a mass shooting than get killed by a gator. But, we all know how to fix the alligator problem from the safety and comfort of our living rooms. It gives us something to think about that has a solution.
Bottomline- I understand why Disney didn't have a fence there. There are tons of places in Florida with gators and tourists, no fences and no fatalities. I understand why the parents of that child thought it was safe, because it was safe 99.99% of the time for the other 99.99% of people who used that beach. Sometimes, you are just that incredibly unlucky person or family who make up the 0.001%. It's not fair, but, last I checked life isn't fair when it's handing out cancer either.