As someone who grew up with the term, the overly-analytical tone describing "thirst trap" is uncomfortable!
You're thirsty if you're horny, typically for a particular person but not always.
You're thirsting over someone if you're horny for someone in particular.
A thirst trap is an act (or video, or Instagram post, etc.) that intends to make others thirst over you. It's like a mating display, but with ulterior motives, if you want to look at it that way.