I'm not sure what it's supposed to be telling about, but it's probably not about their involvement in the war, which was hardly out of line for any german engin

I'm not sure what it's supposed to be telling about, but it's probably not about their involvement in the war, which was hardly out of line for any german engineering company at the time. Ferdinand Porsche was arrested for war crimes, but never tried (which IS telling in its own way). Rather, the NGRAM just traces the rise of the company as it's known today: Up until about 1948, Porsche was a pure development contractor mostly for the government. They only started manufacturing cars under their own brand in the early 50s (a few 356 built basically in a shed notwithstanding) after Ferry Porsche had taken over, and with the introduction of the 911 began a meteoric rise as a volume manufacturer for international markets.