It was clearly an after thought and a bit of a hack, but it works, and it makes it transparent how everything works. I had been taught Java at university before that, and the whole OOP thing was a bit of a hidden mystery. Perl gave me a far better understanding of OOP.
That mindset. Like I said. Did you not read my post?
Steve Jobs wasn't an engineer technically, so he wouldn't know the specifics here, but at the time object-oriented programming had a stigma associated with it because programmers did know of these drawbacks. Using Objective-C was obviously a fundamental choice by the software engineers.
Writing C in an object oriented style is what a lot of programmers did then. But there's a difference between associating data with methods and supporting polymorphism. Hence the talk of virtual function tables.
There were very few fast OO languages and they were emerging at the time. The most prominent examples of those languages are those languages GP names, and they do not exactly live up to the promises of even contemporary OO research, much less modern research.