I don't think C++ succeeded because it was object-oriented. I think C++ was object-oriented because classes were an abstraction that could layer on top of C with fairly low overhead, giving it more expressive power without much mandatory cost to size or speed.

In other words, object-orientation was the means, not the end.

Back then OOP was all the hype and inheritance was cool.

Agreed and that's probably the second major killer feature of C++.