Maybe its something subconscious. Im not that old yet, but from my short experience my fascination in men started before puberty and after my father had died. I hadnt really seen a man naked or anything and i didnt have a male role model, so durring puberty i had feelings about girls, but i also had a want to see men naked. Really, i think i had low self confidence due to not knowing if i was developing properly and not being mannly enough and subconsciously needed a man in my life.
Similarly after my long term relationship with my ex gf i was femaled out and needed attention from a guy.
Maybe its a similar effect, like after being married to a woman for so many years your body beeds some male attention. Idk, i kinda think more people are bi than you would think.
Another effect could be that you are just more open now and dont feel the hold society holds on you, causing maybe some latent feelings to surface. Idk just a thought.