Unfortunately, I can offer some insight.
In the past I have been obsessive. Had I not got help I could have ended up like the stalker in the story.
It starts out innocent enough. Dating involves lots of subtle signals and cues. I remember calling someone many many times in one day, thinking "There's a possibility I'm being strange, but there's also a chance that she's just not home. If I don't call and call again I could miss my chance. And this is my only chance, if I don't make sure she knows I want to date her I'm going to end up alone forever". I'm sure you can see the cognitive distortions at play here. I certainly acknowledged that my behavior was unusual, but I was so fixated on the person that I couldn't stop myself.
I suspect this is what happened with the person in the story. They noticed the sister and became obsessed. First trying to do things "the right way" with super-likes etc within the dating app. After that, finding the instagram and so on. It slowly ramps up. The damage to the car etc I have less insight on, but perhaps it relates to the fact that being ignored by the target of your obsession feels so bad that any kind of reaction, good or bad, would feel better. Or perhaps it's revenge for "making me feel bad". I think the stalker probably doesn't have much insight to their own behavior. I only gained insight years after the fact.
In general, I think dating apps don't help with this kind of behavior. They perpetuate the idea that there are "perfect matches" and that once you find your perfect partner everything will click into place. It's just like Hollywood movies, the couple gets together and then the credits roll. In reality, that's the very beginning. We should be talking about the work and effort that goes into building a relationship, as well as giving people the tools to notice when their behavior is not acceptable.