I get what you mean... the things that makes me like the villainesses or antagonists in stories is being able to sympathize or at least understand their motives and admire their means to achieve their goals. Being cunning, manipulative, strong or even seductive are not things that would make me dislike them... after all they are using any means they can. I think the main point here is that she isn't the main villain, Kirion was. And her getting involved with him or not wouldn't change it. Honestly until certain point in the story I believed she was the main villain, seducing people, sowing chaos between the guardian families and aiming to corrupt the future pope and church.. it even seemed like most od Kirions plans came from her. Until that point I still kinda liked her even if her true motivation was a inferiority complex and wanting a position higher than mc. But from the point it became clear she had nothing to do with the evil side she went from co-villain to villainous side character and as you said her actions and ambitions became too mismatched. A woman willing to see the world burn just to climb up the social ladder. So my like for her as a villainess fizzled out.
Honestly kinda same with mc... evil spirits avoiding her not because of her goodness or willingness to go against everything for the right thing or even faith in god but because she was pregnant? It was like, oh, she's not special, just pregnant... it was a bit... underwhelming tbh... but yeah I agree with you... Delilah started as a good villainess but didn't end so...
I don't know why people like the villainess, and that's considering I've like villainesses who have done more heinous things, as characters. It reminds me of people liking Larissa( from Sister, I Am the Queen in This Life) despite the fact that she sent people to rape and then murder mc, was manipulating people (she's low-key mentally unstable), and also burnt down the imperial Palace of her own country. All for a shallow reason, because she wanted a man. Girl power or female strength can be divided into many different categories, but it shouldn't be about praising others who do things for shallow and nonsensical reasons. I've literally seen antagonist who are similar to the current villainess in terms of being a social climber however, the reason that the antagonist that I'm thinking of did it was a different type of social protection.
I can't remember what the comic was called, but she wanted to raise herself to a position where nobody could bother her anymore and although I may empathize with the antagonist (The antagonist of this story) and the fact that she is a commoner and an objectified woman within society. She could have easily achieved her goals by marrying whoever the first dude was. However, she's running off of greed and power. However, for the situation of the other antagonist who I'm thinking about, she did it so she could be empress and protect herself because she was assaulted within our own home by her step brother and the stepmother turned a blind eye and the father was being neglectful as well and so she did her best to raise herself to a rank and was currently at the point that I was reading the story, was acting as a roadblock for the female lead because she wanted to be empress to get revenge on her ex. And she clearly stated even though she didn't explain her old back story, wanted that all to make position of power which would have acted as protection for her. Versus this current villainous of this comic could have achieved those certain goals under different circumstances, even if she wanted to be a man stealer. However, she wants Fame and a bit of Glory (it's understandable that she wants some sort of retaliation or revenge for people and the men who have used her, to respect her or to be beneath her however, what she's doing is completely unnecessary when it comes to compromising an empire, compromising the lives of so many others. Just cuz you want to prove a point to a bunch of shit bags who's opinions and views aren't worth shit and all the scum upon the earth (which isn't really proving a point since people still won't respect you even if they act out of fear or intimidation))