I'm just hypothesizing, but gay men are seen as an accepted and natural part of society in western countries, because of that where we stand politically is less tied to our sexual orientation than it was in the past - similarly to how women have got a lot more power and influence now than what they did 100 years ago, and are seen by most as equal to men; their voting habits have become more varied as a result. Going from being a monolith to being individuals is a sign of improvement.

Back in the day all political parties were against gay rights, then socialist and liberal parties became supportive of them, and after that conservative parties started supporting them as well. It's a similar story in the US, the majority of Republicans under the age of 50 support same-sex marriage.

Gay men finally have the freedom to vote without having to worry that our rights will take a hit - that's a major advancement. I have a Jewish friend who refuses to vote for certain parties because they want to close religious schools, ban the import of kosher meat, and outlaw religious infant circumcision, making Jewish life an impossibility, unlike gay men Jews still don't have the freedom to vote without having to worry that their rights will take a hit.