"VW's conduct both in implementing these cheats": No Bosch implemented these cheats. If there was help or demand from outside, it was Audi, not VW.
"Why only VW? VW sells more Diesel cars in the US than all other companies together."
The fines should be on all manifacturers of the cheaters. From the list of the affected engines I see not a single one being targeted. The relevant VW engines are all manifactured by Audi, the relevant cheats were manifactured by Bosch, the other relevant cheaters involve everyone: Audi, Daimler, BMW, Skoda, Volvo, VW, Jaguar, Land Rover, Citroen, Mazda, Peugeot, Hyundai, KIA, Toyota, Ssangyong, Infinity, Fiat, Ford, Mitshubishi, Seat, Vauxhall, Chevrolet, Dacia, Honda, Nissan, MG, Porsche, Renault, ... you name it. https://www.theguardian.com/business/2016/apr/23/diesel-cars...
Only those 7 diesel cars meet the Euro 6 NOx limits, the other 97% not.
* Audi A5 2014
* BMW 3 Series 2013
* Skoda Superb 2016
* Volkswagen Golf SV 2015
* Volkswagen Passat 2016
* Volkswagen Scirocco 2015
* Volkswagen Touran 2016
VW's conduct both in implementing these cheats, as well as resisting the investigations into them (to this day!) was obviously, morally indefensible, and totally stupid. Health statistics put the most likely number of premature deaths caused by it somewhere in the 4-digits, in the US alone.
The absolute amount of the fine must have punitive component large enough to make it obvious that such crimes don't pay. At the same time, it wold have been unconscientious to level a fine that would bankrupt VW. I believe the US did a pretty good job.
It also shows a deep misunderstanding of the processes by which the Federal Government works. These fines are not determined by some Trump-like egomaniac impulsively acting on his emotions. Nor is the EPA known to be a fan club of US car manufacturers.
Why only VW? It's quite easy: these manipulations are really only relevant to Diesel engines, which for some reason became a fetish for manufacturers in Germany only. VW sells more Diesel cars in the US than all other companies together.