I feel I might have something to add to this, but I don't really know how.

I felt obsessively in love twice in my life. Both times I was rejected. Both times, that person would still be on my mind for years. If I lost my concentration, I would suddenly find myself fantasising talking with that person. My sexual fantasies would inevertedly switch to them, because any other fantasy wasn't satisfactory. I would have a period where I wouldn't be thinking about them. And then I suddenly would have one dream a week about them. When you do dream about them, the escacy of the illusion of being in their presence is so great, all you can do for hours is try to go back so sleep and hope for the dream to continue.
I also couldn't help save pictures of them and google their names every once in a while. I would also recall all my memories of them, and be grateful of having them. I only send one of them a message on fb, after 7 years of not seeing that person. She didn't reply, but added me as a friend on Facebook months later. Still no reply. I only messaged her because my deep feelings for her died down as they were ignited by another.

So for me, it is not a choice. A part of them lives inside of me and is with me every day. And if feels like they have a puzzle piece I need to fix myself within them. But if they found out, that would freak them out. And as a kid you only learn that love is supposed to be the best thing ever that can save everything. I would sacrifice everything for their happiness. I would die for them, so they can be happy. I couldn't live with myself if I didn't. But all they want is me not to get in their way. So I understand and battle my feelings instead.

I am a naieve person who never touched a woman. All I want is for the other person to be happy, as my happiness seems impossible, at least when it comes to romance. But I understand. If I were them, I wouldn't pick me either.

But the intensity of my feelings must be scary if the other person knew about it. I guess it must be similar to what happens with stalking males. Like I said, I am very naieve. I do not fully understand how vulnerable woman can be. It took me a long time to fully understand that females can be scared of traveling alone at night.
Things like #Metoo remind me of that as well. These manipulating men to seem to be completely lacking from my life. At the same time, it reminds me of how careful woman must be and how that relates to how they may interpret me. If they would detect the intensity of my feelings, that would probably be unsetteling. Especially as some people here say some of these men are really good at hiding how dangerous they can be.

So I would say that you shouldn't underestimate what is happening in someone else's brain. A stalker may be in a positive feedback loop, where they create a fictional version of you in their mind, and that fictional version lives inside them and to them is a real person that they interact with every day. They don't need to meet you to keep the fire going. But all interactions you do have with them can fuel the fire even more. They may take on interaction with you, play it out over and over in their fantasy.