This assertion is surprising. They're not all alike in any way that any two Mac-native text editors wouldn't be. Sublime is markedly different only because it dispenses with Mac-native UI conventions (which IHMO makes it unpleasant to use on macOS).
> BBEdit at the time was, as its name suggests, fairly bare-bones. It had auto-indent and syntax highlighting and very sophisticated grep capabilities, but not much else in terms of programming support. For a long time, it was THE code editor for mac users who wanted a graphical interface but not an IDE. TextMate rose to popularity by mostly mimicking BBEdit, but offering additional programming features like snippets and shell-script based plugins and more sophisticated syntax highlighting (enabling e.g. correctly highlighting CSS and JS embedded in an HTML file).
This seems not quite accurate.
My recollection is that BBEdit was just another Mac plaintext editor app -- solid, but stodgy -- until the Web arrived, and someone built a suite of HTML editing commands for it. That's when it took off. It was the plaintext editor everyone used for HTML until TextMate came along.