You think that LISP and Smalltalk aren't widely used is because they weren't easy to implement in the late 1980's? There have been many languages that have risen to prominence in the 40 years since, yet LISP and Smalltalk remain niche languages.

Which new languages have risen to prominence outside of a niche?

My opinion is that Lisp and Smalltalk are too pure and abstract. C is heavily tied to the real world of computing and can be easier to grasp for beginner. But try to explain variable bindings (instead of assignment) or message passing (instead of function calls) to a beginner in programming. It’s not that they’re hard to explain or understand, they’re just hard to be completely grasped without a foundation in computer science. They’re too alien.