To be honest, that's a change I never bought.
Bashir's reveal, yeah, ok. But smart Rom? Didn't compute at all.
That line doesn't even make sense, early seasons Rom didn't lack confidence at all, he clearly lacked intelligence.
Even post-retcon, he was still extremely thick half the time.
Rom is only tech
-smart though. He's still hilariously stupid when it comes to other things.
After a lifetime of his brother telling him he was stupid, it's no wonder he'd believe him. He didn't have the lobes for business, which Quark saw the be-all, end-all test of worth.