Not trying to defend this ball of delulu or anything, but there's a reason why such hardcore fans exist. Their idols are portrayed as "pure" and "untouched", the ideal love interests pushed by the media for the public to admire and envy. And once this ideal is broken by dating scandals, reality clicks in and leaves fans feeling betrayed and hurt.
That's how Suzy and other idols and celebrities are marketed. Of course, this strategy is universal, but you have to admit it is stronger in South Korea and most other Asian media.