it's at times like these in these threads i hate being a psych major
No idol goes into a fan relationship thinking "Wow it's going to be so easy to manipulate them" unless they've had underlying problems for awhile. The idol does it subconsciously and that's why Lucas was able to get money etc. out of those girls repeatedly, because they probably genuinely had feelings for him (no matter what agreement they reached), when in reality it was just a parasocial relationship. I completely understand why he didn't want to go for other idols because if he was just looking for material things (i.e. money), his partner would probably lose respect for him.