I don’t understand the mystery behind ASMR. IMHO it’s a form of empathy where you recognize, understand, and relate to the situation presented, and experience pleasant sensations as a result. The situations are personal and intimate, and the induced responses match the presented setting similarly to how they would respond in person.
It’s no more mysterious than cringing at someone being poked in the eye — I don’t need to be poked in the eye to recall the sensation when observing someone else having it done to them.
You see someone experiencing something pleasant, and so you relate to it.