45-64 year olds only went for Biden by 1 percentage point in 2020, 49% for Trump, 50% for Biden. And for 30-44 year olds it was only 45% for Trump, 52% for Biden.
This isn't just a problem with old people, even though they're the only group that went for Trump overall. There are still a lot of younger people voting for Trump who won't be dying off for decades. The people who voted for Trump are a slight minority and the minority will be getting smaller over time. But, many of them are hoping that the GOP will break the system so the minority can rule over the majority, even if that means no more democracy.