Simula67 was already known in academic circles by the early 70s. Donald Knuth had first taken an interest in Simula I after a visit in Oslo but couldn't manage to bring it to Stanford because of the very high licensing fees the Norwegian Computing Center were charging for it. That first iteration of the language was more focused on being a general purpose "system description" language for different kinds of real-life simulations (this would also kickstart Nygaards work on the social impact of technology and the beginnings of user-oriented system development, then participatory design). Simula67 however wasn't the "incomprehensible" language that Kay describes. The second iteration was much more focused and had all the elements of modern object-oriented patterns: classes, subclasses and inheritance, objects, object references and attributes, object dot notation, polymorphism, etc.
So Kay's take on Simula being this strange language he had to "make sense of" for his work on Smalltalk, or even the fact he claims he coined the term "object-oriented" is total BS. Here's a more nuanced and impartial account of Simula by James Gosling, if you want to know more: https://www.youtube.com/watch?v=ccRtIdlTqlU.
