The world sure would seem more just if the banks suffered more, right? Unfortunately, it's not that simple.
The loans were made specifically on the basis of Moneual's revenue statements. That is, the banks were trying to learn from mistakes they made last decade, and were relying on audited sales figures to make their loans, rather than "it's a technology company, it must be magic" like they were ten years ago. Unfortunately, the company lied about its sales figures, and then the auditing firm confirmed those falsified numbers. I'm not sure why the banks involved "should" have known that Moneual was lying and the auditing firm was incompetent. Maybe it's different in South Korea, but in the U.S., that kind of screwup would put the company's executives in jail for many years, and would lead to crippling fines and lawsuits for the auditing firm (how's Arthur Andersen doing these days?), so income statements and balance sheets tend to be considered fairly trustworthy.
Furthermore, bank loans like this are almost always collateralized by company assets, so in the event of default the bank gets first go at anything left over. Only large, well established companies can get away with issuing unsecured debt without crippling interest rates. Secured debt is precisely why lending to a startup (the Korean parent company is only four years old) is not a "foolish risk." Seriously, think about a world in which banks were not allowed to recover assets from their debtors. Why would any bank issue a loan, or at least a loan without double digit interest rates?
Actually, you don't have to imagine this - just look at the interest rates on a credit card, which is unsecured by any collateral. And before you tell me that those rates are so high only because banks are greedy, compare the credit card interest rate to the interest rate on a mortgage. Both credit cards and mortgages are issued by the same greedy banks, yet one usually has an interest rate of 15%-20% while the other has an interest rate of 4%-5%. The main reason for this difference is the fact that the mortgage is collateralized by the underlying house. That is precisely why lending $200,000 to a couple that makes $60,000 a year is not a foolish risk; the bank knows that it can get most or all of its money back by foreclosing on the house.
And lastly, how would you feel if the same logic got applied to every other fraud victim? Do you find it just as easy to say that the victims of Bernie Madoff "should" have known that something was suspicious, and that those investors took a foolish risk and should suffer the consequences? Why should these fraud victims (and make no mistake, the banks are fraud victims in this case, according to statements from at least one Moneual's own managers) be treated differently just because you don't like them?