Major unpopular opinion, ik. I don't agree with them but understand. Firstly many idols sell the boyfriend image. E.g. in fan-meets if a fan ask "will u marry me" etc, many idols say yes. In an outsiders perspective, ofc its dumb to believe that they mean it, but companies know there are fans who buy this "pseudo-relationship" concept. There is market for this and they capitalize off it. These fans will often also be the ones that spend the most money on the idols. In fact idols in general gain many fans through fanservice.

For idols that don't sell this image, they get less backlash in comparison but still get backlash. I think its due to a lot of people stanning idols for liking to see them work hard, achieving their dreams. You want to help them achieve that dream. So fans get mad when they're dating (esp. in shows like produce, where they're basically trying to show they're desperate to succeed). In asian culture, a reason why parents try to prevent their child from dating in school is bc there is still a stigma that if you focus on one thing it'll pull attention away from you doing your best in the other. If you date then you must not be that desperate for your debut; bc the time you're out on dates other trainees are still working hard in the practice room. That's also why after idols reach their peak of their career, they don't get much hate for dating anymore --- their image is no longer "someone so career-orientated/desperate that they're willing to put everything else on hold". Again i personally don't share this view, I just see why they'd react this way.

The reason why so many fans leave the fandom when dating news breaks out (for rookies) is probably because many of them only entered the fandom believing in this "fake-relationship/desperate to succeed". If companies really wanted a healthy fan-idol relationship they shouldn't try to make money off things promoting the opposite. (Yet they know logical fans spending less = less $$$ for them sooo). Crazy fans that buy into the delusions should definitely self-reflect. However, considering how the target audience for idols are younger fans (minors that r still immature), I honestly think business/idols profiting off by selling this delusion has equal, if not more responsibility in such behavior resulting.