It’s like if you like a band. And someone asks you why you like them, and you can’t really explain it. “There’s no reason to it. It’s in the soul of the band.” And then some music critic comes by and says maybe you like them because of their relatable lyrics, their catchy production, the perfectly timed hook, formulaic tricks that make it sound familiar etc. Well, that makes the band feel a little less special now. The idea that another band could become your type instead of it just being some cosmic fate that’s channeling through you. It makes the band feel less special, it makes you feel less special, it makes the whole concept feel less special. That’s "the spark" in a nutshell. Women struggle to explain it, but some nd manospherian will probably correctly point out how there are men with a similar cluster of traits with whom women just "magically" feel "chemistry" with even if she only saw him once at Coachella, and men who can't get a single woman to see him as anything more than a "brother" no matter how much of a "great guy" they think he is.