Pretty simple:
1) Pac-12 was a Johnny Come Lately to the cable industry, an industry that began its decline around the same time Pac-12 Networks was formed.
2) They are too aggressive with their content production. With 14 members, the Big Ten Network produces less games a week than Pac-12 Networks.
3) Big Ten Network was partnered with Fox Sports, which permitted them to use other Fox properties like YES and the various Fox Sports RSNs as leverage to get onto basic tiers of cable. This is where the real revenue is; had this gambit failed Big Ten Network would also have failed.
4) The article fails to mention The Longhorn Network, which is broadly regarded as a failure despite backing from ESPN. Reports are the Longhorn Network has cost ESPN $48 million more than its revenues in its first 5 years.