For those who have broken off a relationship, leaving a former partner behind can be painful for both parties. The person who was left sees it as a failure on their part, but they might not realize the person leaving them did so for a good reason. They might have seen the attachment was wrong, but they recognized it was growing too fast and needed to be cut immediately. When a person who has been left refuses to stay away, the mistake of giving in for one more meeting or date could encourage them to become a stalker.
Emotional attachments are difficult when they are not successful, and each person will bear their own pain when they end. The person who becomes obsessed with a former partner is out of control emotionally, and they do a good job of rationalizing their behavior. If they find even a small opportunity to get their former partner to meet them, they will continue to push to get the relationship back.
The person who broke off the relationship due to an obsession by their former partner would seem to know it is a bad idea to ever agree to meet them again, but they might still have feelings for that person. It could seem innocuous to meet for coffee, but they do not realize the depth of the danger they are facing. Just one cup of coffee shared could turn on the faucet of depravity in the other person who feels angry because they have been left behind.
Stalking is not about an emotional attachment between two people, and that is part of the danger. While the stalker generally knows their victim quite well, they can give it the appearance of an emotional attachment when they are actually living in a dream about a relationship that never existed.