Maybe they're simply retiring the inferior technology under the existing, and premised, rule-sets?
2011: Audi - 2nd
2012: Audi - 1st
2013: Audi - 1st
2014: Audi - 2nd; Porsche - 3rd (Toyota Hybrid winning)
2015: Audi - 2nd; Porsche - 1st
2016: Audi - 2nd; Porsche - 1st
I think VW's spending has been an excellent use of resources. They've been able to assess existing (Diesel) and more cutting edge (Hybrid) power trains in the wild, while spending way less than would have been the case had they jumped into F1. Both entrants were competitive, they've won championships, enjoyed increasing exposure, and avoided the bad publicity that is generated by lacking competitiveness (Nissan in LMP, Honda in F1).
The Diesel-gate crisis probably did necessitate a rationalisation of their Motorsport expenditure, and its very convenient they can 'drop' the diesel-based team, without losing their ability to win championships in this racing category.
The move to Formula-E is a savvy PR move in the context of their recent public faux-pas, but holds no major significance beyond advertising, unless the rules of that series are relaxed to allow greater competitive advancement of the battery technology.