Yes. I was one of the first Justin.tv investors. I think my final return was about 97x, so that's pretty good.
From my perspective at least, Twitch was essentially a re-branding. Basically, they saw that gaming content was popular on Justin.tv, so Emmett decided to move that on to a dedicated site. Ultimately Twitch far eclipsed the justin.tv site, so they shut that down to focus entirely on the Twitch side.
Based on the Startup School podcast episode I heard with Emmett, it sounded like it was less that gaming was popular (I think he said it was 2% of traffic) and more that it was the only content that Emmett actually liked watching. (Not trying to disagree with you, given that you were there, more trying to give another perspective.)
I dont see how it couldn't have. Twitch was almost undoubtedly built on the JTV tech stack and staff. Also consider that Amazon owns the justin.tv domain.
I know that Twitch was sold, but I heard that it was completely separate from Justin.TV