[rbanffy]

> closed nature and hard to integrate with existing tooling (editors, vcs, OS)

This is probably the big reason - Smalltalk is its own OS and GUI, and didn't play well with others until relatively recently.

> poor story for Web, Java had applets and JS was native

This only became relevant after Smalltalk was already very niche.

> slower and memory hungry compared to C++

So was Java back then, and, thanks to free-as-in-beer and being easier to integrate into build tooling and the workflows developers were used to, it had a much bigger impact.

> lack of type safety compared to Java/C# or Ocaml

The way Smalltalk works, this is more a feature than a bug. It's a given it'll result in more runtime errors if types are abused, but that's also one of the reasons so much early progress on automated unit testing started there.