I am very much like you! I have what I call "rapid fire" special interests where I will have a very intense interest for a few weeks, maybe months, and then I will totally lose interest again. This is most frustrating when it's a new hobby that needs equipment which I buy and then end up with a bunch of stuff!
A while ago a friend suggested we needed a neurodivergent hobby-swap club!
I also have a few long-term special interests that have stayed over the course of my lifetime, but these are quite rare and few.
I, too, have people still share stuff to me from a special interest I had about 12 years ago, and made a post on facebook about how excited I was about this thing. I'm kind of honoured that people remember, but it also confuses me still!!