This doesn't seem to be anything special about Hypercard. Hypercard was the BASIC of the Macintosh in that it served the same niche. It certainly was not BASIC, but the idea was the same, a little language and environment that fit into the machine's environment that allowed novices (and then highly practiced novices :-)) to create stuff on the machine for other people to use. It was killed for the same reason BASIC,…
Hypercard was mostly useful as a sort of personal wiki or address card book; I used it quite a bit as a notepad with hyperlinks. It didn't die for any real dramatic reasons. It was programmatically stuck in the 9" B&W Mac era and never quite fit onto larger color screens, so once the web came around, Apple dropped it.
Also you history is way off, because BASIC morphed into VisualBasic, which did everything Hypercard could and ten times more, and was the leading programming environment for a generation.