I think there's some level of interest in that tech jobs are fairly cushy (can work from home several days a week, benefits are good) and most older SWEs usually have more of a passion for the field. There's also maybe more of a culture nowadays of continuing to work at least part-time through typical retirement age to keep your mind active.
With Harry Potter (and Star Trek, I believe) fanfiction, I think decline in quality has been typical for the last decade; the fanfiction from the 90s/early 00s is often of much better quality on average just due to the age + other factors affecting who was able to type up and post fanfiction online back then.
[1]https://www.cremieux.xyz/p/why-are-testosterone-levels-risin...