I've written extensively about the history of Smalltalk. In those articles, I explained when Smalltalk was a major market leader and why it fell from grace.

In a nutshell...

- Smalltalk was wildly popular in the 1980s and early 1990s.

- The rise of Java derailed Smalltalk's future.

- Smalltalk also had a reputation for being expensive, resource-hungry and not ready for the Web (all of which have been fixed but too late).

Functional programming is far, far from replacing OOP. Most enterprise software are still written using OOP.

Concurrent programming is somewhat niche. It's used for certain server applications. Most software do not make use of concurrency.

The vast majority of applications are not performance-sensitive, which is why most of the Top 10 programming languages are not high-performance tools.

Smalltalk syntax is very, very simple and elegant. It's not hard to wrap your head around it at all. Even children take to it easily.

Read one of my recent articles: https://itnext.io/celebrating-50-years-of-smalltalk-172d4e664d30.