Markets will trade with, or without, integrity.
I recall when a seat on the NYSE could not be held by a corporation; as a partner's (or individual's) full financials would be on the line (up to their domicile).
Those were the days of integrity. Commodity firms held even higher standards.
Such has not been the case for more than a few decades.
Did the markets function without this integrity?
Obviously they did.
However, it takes a while from the commencement of the storm to the onslaught that ensues.
MF is just one example.