It's probably just a move to show that they 'legally' allow their customers to use the bank account for cryptocurrency-related activities, hence why they charged money. In the end, it's just to get more money.
Yes, it gives me a chuckle to see they used the word 'legally', lol, it crypto illegal in Belarus? I thought they are just friendly and welcoming to crypto? In any case though, nothing to lose here, if they used Belarushbank to acquire crypto then fees are definitely charge to customers. You can acquire crypto and then hope that you will get a decent profit to cover those fees and expenses.