Create a fake passport to travel under your name and commit crimes. Try not to be surprised when you discover an arrest warrant in your name for sex trafficking in Belarus.
Truth is, lots of extremely sensitive data exists in insecure states all the time.
So, yes, I draw a distinction between numbers that we hand out willy-nilly and truly sensitive information. There's a big difference between my checking account number and my health records.
This would only require a name, not a passport number. A passport number would simply be of no use here, there doesn't exist any¹ automated mechanism for Belarus to verify foreign passport numbers.
¹Well OK, with biometric passports it is possible to cryptographically verify some data.
At least right now the NFC chips simply have no effect on passport forgeries.