>>50918830>>50932938This happens as a side effect of child fans growing into adult fans. This can be seen with any IP really but it's seen especially in Pokemon because the brand actively tries to get children attached to the property with the pitch that their journey as trainers grows and continues as they grow. So, as kids grow into horny and sexually cognizant teenagers and adults, they begin to look at the things that they like in a more sexual way. The kid who once thought that Cynthia was the coolest champion now notices that she also happens to be sexually attractive as a young adult.
Really, it's the same as how a lot of Pokemon fans want Pokemon to have darker, more adult storytelling and worldbuilding as they get older because they begin to look at stories differently.