In response to the OP, I think a lot depends on how you define “homosexual.” Also, are you asking about all homosexuals or just some? I’m influenced by the Kinsey report (the basic concept, not necessarily the supporting details) in thinking that a certain percentage of the population is strongly heterosexual, a certain percentage strongly homosexual and a large percentage on a scale somewhere in between. Those who are able to change probably are closer to the heterosexual side to begin with, have a desire to change and can also make a clean break with their previous social groups.
I also think some people are labeled homosexual and believe it, when in fact they are not. Of course it would be easier for these people to “change” than someone who had more deeply seated, long term tendencies. There are the typical stories about being recruited or seduced, but it wouldn’t surprise me if the American obsession with masculine stereotypes didn’t lead some men to believe they are homosexual when in fact they just desired masculine bonding and friendship. They don’t know how to interpret these feelings and assume they are homosexual. I’m reminded of time I spent in Europe during college. Physical space between people was different. It wasn’t unusual to see men hanging out at the pub drinking a draft beer with their arms around each others shoulders. In some cultures men walk arm in arm or even hold hands and it is nothing more than friendship. As a grown man Abraham Lincoln supposedly shared a bed with his friend, Joshua Speed, for a number of years while he was a circuit attorney, but it was nothing but friendship. Yet if men in the modern United States did any of this they would be labeled, harassed, called names or even beaten in the street for being homosexual. Men in this situation might believe they are “homosexual” when in fact they are not.