Why Would the NSA hack the global Banking System?

If this is true the reason would be that since Nuclear weapons cannot be used (unless North Korea uses them first) the next big war on earth will be "wiping out all financial records on earth" by one of the major powers.

Why would they do this?

To Bring to their knees foreign powers who are their adversaries.

So, that all records might be lost and if there aren't backups present there would be possibly no way to straighten out world finances at all.

some of the ramifications of this potentially:

Governments collapsing.

People rioting in the streets because no one has any records of their banking.

Businesses going bankrupt worldwide because of no money for payment of debts.

Chaos.

So, this goes beyond a "TRade WAr" this is likely the next big World War and how it would be conducted by Russia, China or the U.S.

These are the only players big enough to win such a war against each other.

What countries are the most vulnerable to such a war?

I would say that China and the U.S. are the most vulnerable to such a financial war.

This goes way beyond a trade war because there can be no trade if bank records are wiped out in any country or countries beyond a certain point.

For example, all bank records are "Magnetic". Magnetic bank records whether they are in a hard drive of a small computer or large mainframe or kept as backups in tape or removable hard drives or other such recording backups are all vulnerable to EMP or "Electromagnetic Pulses".

So, one country could easily end all financial records of banks in another country therefore by wiping out all hard drives AND all Magnetic media records of any bank unless these records were over 10 feet underground by setting off EMP devices in any city in the world where they wanted to end the usefulness of those banks permanently or temporarily to the point where all bank records of the previous month or year were permanently wiped out above ground. (above 10 feet underground).

So, in regard to North Korea this actually could happen now worldwide if this gets out of hand right now because North Korea takes it there the U.S. would also respond and wipe out whatever country or countries attacked the U.S. in this way too by wiping clean all record of their financial transactions too in retaliation.

Note:
As I thought more about this there are only two ways I presently see to avoid this kind of problem eventually.

either all records are backed up daily to something that isn't magnetic Storage like a DVD which works on a completely different principle than magnetic storage. OR I suppose you could also use Hardcopies of your daily transactions at any and all banks. However, that would be reams and reams of paper over time and then you would have to store all that too. So, something like a DVD or reburnable DVD daily might be the best outcome for all transactions of any one bank on any one day worldwide. If a device was built non-magnetic that served the same function as magnetic storage but was more like a reburnable DVD say equal to 100 or 1000 DVDs each bank might have a back up taht would be there even if there was a power outage or even an Electrmagnetic pulse. Non-magentic DVDs, for example, are sensitive to heat and can burn in a fire but otherwise are relatively unharmed by electrical interference of any kind. So, it wouldn't matter if they were stored 10 feet underground or not.like it would with magnetic storage devices tapes for example.