@revelette2,
We are a country which is still digesting decades of espionage at the hands of the East German Ministry for State Security (Stasi), not only during the Nazi-period. And thus, the issue stirs emotions.
The main points currently being held against de Maizière (and Merkel) is that last month he went on record saying there were "no findings relating to alleged industrial espionage through the NSA or other US services in other states."
But according to various media (and that had been more orless confirmed by now) at the time of that statement, the German government was already aware of "attempts by the NSA to use an existing cooperation to explore German and European companies".
And now people (and the media) are asking: what more was given to the NSA?
Making that information accessible enough to provide a fuller picture is, given its very nature, inherently difficult. But there's no doubt that this scandal has the potential to be damaging to the interior minister's (at least his) political future.