The reintroduction of faction locks is a result of player lobbying and vigorous debate.

Numerous examples were provided to ZoS showing how 'faction-hopping' permitted a number of abuses, several of which violated ZoS's intended Cyrodiil gameplay.

In the patch notes for Update 18 (Summerset), ZoS stated they "were still looking at concerns regarding Alliance loyalty to Campaigns". Granted, unless you read every word of every patch note, that statement could easily have been overlooked. But many of us who advocated for a reintroduction of faction locks in some form - to address the damage to competitive play - took that as a sign that the issues raised by players would result in some sort of action in the future.

So as far as I am concerned, an option to play in a competitive campaign, where scoring matters significantly to rewards, has been long overdue.

While many seem surprised at the change, those of us who have been involved in advocating for reintroduction of faction locks are greatly relieved.

ZoS also stated (more recently, during E3 Twitch, I believe) that faction lock is a global condition that can be set for new campaigns, and that they'd be watching how this experiment plays out.