Some of this has got to be the fact that macromedia flash originally was more targeted to artists and it was dead simple to create nice 2d animations. AKA it wasn't a programming environment so much as an artistic tool. The current version (adobe animate) doesn't seem nearly as popular despite the fact that it can apparently target html/canvas. Part of that just might be fragmentation, with wick editor, opentoonz, there isn't a single tool everyone talks about. Although I'm not sure if those tools can legitimately "grow" into programming tools the way flash and now animate can. (aka the artist draws up a bunch of stuff and then needs to learn some programming or have a programmer to come along and fix the donate button so it actually takes money like was possible with flash).

OTOH, I used to know a bunch of artistic types that had pirated copies and would sit around and create flash animations for their bands/etc. Now those people just do video editing and post things to youtube/etc, or spend time editing photos for facebook/etc. There isn't a hypercard/programming aspect anymore buried under their tooling.

edit: actually it looks like wick can do the hypercard/flash programming too, which is sorta cool.