I like the “music from the 60s is just plain better music” theory to explain why youngsters nowadays have nostalgia around that music, personally. I mean, afterward, you have music from the *70s.* No competition!
The 80s nostalgia bump is probably part of a larger blob of media in general that was consumed and preserved in an unprecedented manner due to things like VHS existing, and The Breakfast Club being a f*%^ing awesome cult classic.
I fully intend to take this survey at some point, though I will confess I haven’t yet. Further commentary may occur after I do so.