What happened
In the days immediately following the NSU's exposure, an official at the Federal Office for the Protection of the Constitution ordered the shredding of files relating to far-right informants — a decision that, whatever its stated justification, destroyed evidence relevant to a live investigation into a decade of murders and drew accusations of an active cover-up rather than mere incompetence.
Subsequent parliamentary inquiry committees (there would eventually be several, at federal and state level) concluded that institutional failures were systemic: information silos between federal and state intelligence agencies, a reluctance to conceive of organised far-right terrorism as a serious threat, and use of informants who were themselves involved in the far-right scenes the state was meant to be monitoring.