"So the question is whether we want to try to prove infringement on all those products, orbe satisfied with 42 million simply proving Kindle infringes? The choice seems obvious to me. The rest of the infringing products are still there."

I agree, it's easier to get 42 million than 130 million from one company.
And most important: it's easier to prove Amazon's infringement on the Kindle produced by Amazon (or on behalf) than on the other products Amazon only distributes.