Netflix is, of course, the king of streaming media and CSTV was small (and ended up being a total disaster), but that doesn't make them an expert at producing and broadcasting/distributing live sports. I'm not saying Netflix couldn't pull it off, there are advantages to BYU signing on with ESPN.
As far as the potential of streaming of live sports, I would bet on the model that's already starting to emerge with ESPN allowing Sling TV to stream their broadcasts. IMO, the barrier-to-entry is higher for Netflix or some other company to convince sports leagues/conferences to ditch their existing TV partners than it is for ESPN to just take their existing content and start streaming themselves and/or partnering with streaming providers (including Netflix, potentially).