A billion dollars is not bad for a site that started as a fake-it-til-you-make-it piracy site. I only know the story 4th-hand. But, my understanding is that it started as a user-upload site (I.e. piracy with disclaimers). And, of course, the seed users were actually employees with puppet accounts pirating media to their own site.
That kicked off real users who competed on getting the highest quality subtitle jobs uploaded quickest after the first broadcast of a given show in Japan.
Once viewers outside of Japan learned that they could get episodes same-day as Japan, they flocked to CR. Of course, this was only possible because CR did not attempt the impossible task of convincing the producers to allow this to be possible.
Once the CR audience was high enough, there were two obvious consequences: 1) They were too big to fly under the radar and were likely to be sued soon. 2) Their audience was large enough to be offered in negotiation with the publishers for a legit contract. So, that's what they did. They offered a fair revenue split with the publishers in exchange for being a legitimized distributor.
There are lots of ways that this could have gone badly. Most piracy sites do as much as possible to exploit the material and the viewers for short-term gain. Most publishers reasonably lawyer-stomp such sites as fast as is feasible.
But, in this case it worked out. There's no way CR could have negotiated with the publishers up-front. They were starting with nothing at all to offer. No audience. No reputation. No capital. Nothing.
Their approach was not legal. But, it was small and respectful-ish enough to not be worth suing until it was large and respectful-ish enough to be worth negotiating with.
Do not recommend this business plan. Glad it worked out for them.