My honest take:
It started out being a kid on forums back in for late 90s early 2000s when posting surprise shock pics. Those used to be really upsetting and i remember thinking that I didn't want something to exist that could make me feel so horrible so I tried to desensitize myself to it. Then 9/11 happened live while I was in the computer lab and was glued to the SA and Fark threads were they were aggregating all the footage they found. I was also a CNA and beginner EMT when I was in high school and was exposed to more death in person. I don't get any sort of sexual or drug-like pleasure or any sort of feeling that I want to act out what I see, but something about the vids hits the animal part of my brain and fascinates it. Fascination is the best word I can muster that works. We have such a clean, sterilized society in the west that it serves as a reminder of how bad life really can be. There's a reason why traffic slows down in the lane opposite a big accident and it's because a part of everyone wants to see the carnage.
But there are limits. I can't stand anything with young children or women or animals getting hurt. I don't like torture videos where it is brutality just for brutality's sake. The accidents are what interest me in the most, This whole thread is a great instruction manual on how to not fuck up and get killed. I've even had to talk friends out of doing stupid shit like jumping off a balcony into a hotel pool by telling them about how many videos online there of of mangled people with their brains hanging out. Or de-escalating fights because you never know when the other party is going to whip out a knife or gun and end you. Maybe there is something wrong with me and this is all weak rationalization but I dont think consuming these vids has had any sort of negative effect on me.