I never understood the obsession over this - she was under no legal obligation to do so and as an attorney, she's trained in worst case scenarios. Pedes on this site have said wouldn't it be funny if she did resign & then the election was overturned - she knew that.
to some extent it's a practical matter; it is thought not to be good policy to allow it as all you would have would be counties suing and cross-suing each other over every political, economic, environmental, etc, disagreement.
the italian guy's affidavit has to be balanced against other facts, from other sources. anybody can swear to anything with little fear of prosecution if the affidavit is contradicted by other more persuasive evidence & deemed non-material. i don't know wtf, if anything, happened overseas because no on purporting to know has brought forth sufficient proof. evidence is not a where-there's-smoke-there's-proof type of thing; even if there's a lot of smoke.
holy sh*t - just like that? she got her publicity & off she goes.