The short answer appears to be that once you get past factors which are visible to the naked eye and which everyone agrees on (it's better to be thin than fat, rich than poor etc), romantic attraction appears to be almost entirely idiosyncratic and unpredictable, even among identical twins: https://slatestarcodex.com/2016/10/21/the-heart-has-its-reasons-that-reason-knows-not-of/ http://cogprints.org/773/3/155.pdf It seems possible that this may be an example of a scientific question that is essentially unanswerable as the answers will be mostly the "crud factor", at best explained by effectively undiscoverably complex interactions like epistasis and evolved, like personality, for that reason (see Penke & Jokela), and one might even wonder if it is an example of deliberate developmental instability which evolved as a kind of bet-hedging.

You could also ask: Can bicycle riding be explained? What factors lead to bike riding? Proximity, physical attraction, happenstance, personality, wealth, health, values, shared experiences, individual preferences?

You can likely run correlations with those factors but they are not going to explain you much about the nature of bike riding.

Reading Mate by Tucker Max and Geoffrey Miller might provide you with a better perspective on the subject.