I think it’s for many different reasons, but a bit the same as everywhere. Some are protest votes due to a distrust in government in general, then 35-45 is the age most get kids and in contrast to their parents generation they live in apartments, not single family homes, as houses aren’t affordable. Then there’s the general widening of the wealth gap and the populists pretending they have a solution and blaming it on immigration (while themselves being a big reason for the problem in the first place…), while left parties often get tricked into reacting to right rhetoric, letting the right dictate the discussion. Old people are less affected by the wealth gap, young people don’t have kids so they don’t notice yet. And in it’s also a question of mobilizing ones base, the right parties get a ton of money for ads and so on, they are good at stirring up fears of existential threats(which is ironic given the real existential threat of climate change), while a lot of people are disillusioned, so middle aged left voters are less likely to actually go vote whereas more right voters do. Of course <30 voters worry more about climate change and are more motivated to go vote, since they’ll be the most affected by its effects.
I’m sure there’s many more reasons but these are the first ones I can think of off the top of my head.