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,…
1) It was a concrete implementation of the idea of hypertext that actually worked. The fact that comments in HTML begin with 2) It was the first graphical IDE that I know of. (Clunky? At the time -- 1987 -- it was glorious.)
3) It was one of the easiest programming languages to pick up, if not the easiest, and yet it scaled to become quite powerful. (There was eventually a native compiler, itself written in HyperTalk, that could even create INITs.) HyperTalk's ease-of-use led to blind alleys (AppleScript tried to one-up HyperTalk and ended up being "read only").
4) It was extensible via plugins.
It was also an incredibly productive programming tool. In addition to allowing novices to code, it let me -- for example -- implement an RDMS engine in an evening, and build a database application (including reporting functions) in a second evening. It allowed the Millers to create Myst (they used a couple of plugins, one to display color images).
But HyperCard was written by a lone genius (Bill Atkinson) with weird quirks and flaws and it was impossible to maintain or improve. Its notable flaws included:
a) Weird code-base. It never really got a version 2.0. This is probably its single biggest flaw since all the others are things you'd have expected to be fixed in later versions. (Yes I know there was a version 2.0, but aside from a new debugger and plugin interface it wasn't a big improvement and it was slow coming.)
b) No native support for images. Visual Basic would address this by allowing you to treat images as just another kind of variable and manipulate them directly.
c) No native support for color, and 1-bit graphics were built into it in a very hard-to-fix way. Indeed, HyperCard was rewritten from scratch for the Apple IIgs and worked fine in color, but the Mac version never did.
d) No support for native controls. All of HyperCard's controls were faked and looked wrong. (And this flaw was faithfully copied by HyperCard's many imitators -- such as SuperCard, Runtime Revolution (still going!), and Assymmetrix Toolbook.) Again, VB addressed this.
e) No ability to create true standalone applications. Once again, VB addressed this.
HyperCard wasn't killed by Steve Jobs. It withered on the vine and Steve Jobs simply took it off life support. As for the other stuff he killed -- yeah, some of the dead-end Lisp-based projects that hadn't already been killed. No conspiracy -- HyperCard just wasn't fixable and by 1997 it didn't matter any more.
Several HyperCard clones went on to be pretty successful. Macromedia Director came into its own when it copied HyperTalk (which became Lingo). Visual Basic was in essence an improved HyperCard but with a crappy language. (In every head-to-head test I tried between VB3 and HyperCard, HyperCard hugely outperformed VB3, which if you know anything about HyperTalk is pretty sad.) And then of course there's the whole web thing.