There's only one way to do a "noble demon" reasonably tbh, pic related. It's to show that people don't have an inherent nature that's good or bad and despite being "born evil" you can still be good. The usual version of the trope is literally just simping for a strongman bad guy because he has some admirable qualities despite being clearly and on the whole a bad guy. Which is both ridiculous and pathetic. It doesn't matter if the villain has admirable qualities or carries out their plots "ethically" if their plots have a nefarious purpose. The trope is basically liberalism distilled. You can pursue whatever ends you want just as long as you play by the rules (somebody's rules) and are polite about it.
The reason for the archetype being so popular is more nuanced though. It's become passe to have a villain who's just outright evil and malevolent. You even see goofy stuff like Disney making movies for villains making them more sympathetic (most recently with Cruella deVille of all people). That's because while the audience might get to root for using force/violence to beat the bad guys, they MUST feel bad about doing it. We can't really have someone just be bad and wrong and need to be stopped. You gotta keep that trump card in your back pocket that everybody deserves sympathy (at least the named characters) in case the commoners ever see you as the bad guy.
Another aspect of it is that people tended to sympathize with villains even before they started actively making them sympathetic, since they are more interesting characters usually. Heroes tend to be ciphers who are largely content with life besides the villain messing things up. Villains tend to have texture and to care about things and to have some kind of struggle to pursue what they want. That's a lot more dynamic and interesting inherently but it's also a structural issue for someone in the business
of storytelling because by positioning anything as the villain you risk people thinking it's cool. That's a large reason why the political content of mass media has shifted away from overt propaganda, because it doesn't work. Not just because it's cliche but because you risk making your political enemies seem appealing. And obviously you can't make the "bad guys" into the relatively boring protagonists unless you want to get baroque. So the obvious thing to do is to have fictional politics that are vaguely inspired by the real world but that can't really translate into the real world in a meaningful way.