>>53183480>Eternal youth is part of his motivationEternal youth is metaphorical.
His goal is to create a sustainable society, which in his twisted mind meant culling humans and wiping out Pokemon (yes, he wanted to kill all Pokemon, even his own, people forget that detail). He believed that unchecked population growth would inevitably lead to war and over-consumption of the world's finite resources.
Team Flare's obsession with beauty was mostly them misinterpreting Lysandre's words, believing that they were chosen by him for being beautiful people, when in reality they're just some spoiled rich fucks and Lysandre was an unironic "just stop being poor" elite who blamed the have nots for being lazy.
