Why did Sulli decide to do exposure scenes in real life?

‌I had a feeling something was off when I saw her Instagram posts after she started meeting Choi Ja..
Is there really a reason for a top idol of that era to risk exposure?
I feel like Sulli took a harder hit than Kim Soo-hyun did...
I used to think Sulli and Krystal were on the same level visually in their group,
but seeing them both as actresses, Sulli completely overwhelmed Krystal's looks.