Seems clear enough.
As being gay is less reviled, the chances of noticing, thinking about the matter, and socializing with admitted gay people grows.
Opportunity, curiosity, or if even if initially disinterested, meeting a person that draws your attention, be it cerebral or physical, against all your mores.
Then unplanned / unexpected events may follow.
And of course, some people will get into it for whatever reason, some clueless/bored/bold people always try anything with whatever results.