Z-Machine is also useful to point out because it's one of the clearest lines to draw from it to the modern JVM and .NET CLR. Whereas AGI/SCI/SCUMM all have very game specific virtual machines, Infocom's was Lisp influenced and even built it with business/enterprise apps in mind, though Infocom's one attempt at doing exactly that with their database app Cornerstone was a market flop. (It's heavily enhanced fork of the Z-Machine was also only released for a fraction of the machines the game Z-Machine supported.)
I still think it's an interesting question if Infocom had not tried to keep the Z-Machine proprietary "secret sauce" if it would have been a larger platform of general computing for much longer and broader than Infocom's own lifespan and primarily games focus. If Infocom had taken a Sun-like stance on the Z-Machine being a JVM ahead of its time and building a broader compatibility ecosystem "write once, run everywhere" might have been an earlier part of computing.