Apparently a group was going around burning things in Germany, and publishing long tracts about their acts. Linguistic analysis seemed to link those tracts to her husbands research papers. The whole "7 words" quote seems to be a (wilful or not) misinterpretation of facts : the writing style was probably similar.
As someone else mentioned, this person used to be a squatter in East Berlin in the 90s , so one could guess a bit of an anti-authority type. At least that's how the reasoning could go.
No, they were "tipped off" by some Google searches they did at their own desks. There's nothing to suggest that any surveillance of private communications (by any agencies) had anything to do with the initial investigation. Nor was there anything "high-tech" about the research the investigators did before obtaining their warrants (beyond using Google).
