We've discussed it and it's been debated a lot elsewhere is that Warner Brothers has had a lot of trouble setting up this new movie universe, because of the following:
-While WB does own DC, they cannot allocate all their resources towards making comic book movies, there are other people with their own projects that also need funding;
-There was a lot of difficulty setting up a pseudo internal "DC Comics Movie Studio" since so were so many people with their hand in the jar;
-WB lost it's confidence in Akiva Goldsman, who used to be their old go-to Super Hero Movie producer and as such hadn't found their Kevin Feige yet;
-WB, during the early Marvel movie build-up, was still very much stuck on the Harry Potter / Dark Knight money train to have any strategy and really who could blame them, since both franchises were making a lot of cheddar?
Now with regards to what was the trigger, I don't think it's was just The Avengers and GotG that made DC Comics finally do this:
-Man of Steel, love it or hate it, was sucessfull enough to invest more time and resources into comic book properties;
-The Arrow TV Show I think, also boosted a lot of internal confidence which has prompted them to also invest more into TV-themed Super Heroes, an area in which Marvel is still very much has no footing, in this era of HD TVs and people preferring to watch more stuff at the comfort of their own home, it's a smart strategy;
-The overwhelmingly positive reaction at the announcement of Batman vs Superman was also encouraging;
Now with regards to the actual lineup, I was only a tad dissapointed that Shazam! is only a 2019 release, since Dwayne Johnson has been so vocal about it, I was under the impression that it was a more immediate project.
Kinda of a shame, since I'm super into the character right now, dare I say, almost as much as Superman vs Batman.
Also to note, unlike Marvel who wants all the TV Shows and Movies to follow an ubber cohesive timeline, DC's answer to that is: Screw it!
Screw it, TV Universe and Movie Universe will be separated, because (IMO):
-We expect our audience to be smart enough to understand that the Bruce Wayne from the TV Show Gotham has nothing to do with the Bruce Wayne on Batman vs Superman;
-Separation allows a bit more creative freedom which is something that's starting to harm the Marvel Universe a tad.
