It is just a coincidence that a few weeks after BVS opened, Warners did a major shake up at the DC film division,and brought in Geoff Jones from the DC TV division to make major changes in the film division. ...
And it is also pretty clear that Warners was keeping a tight leash on Snyder directing JL. That a few days into production they removed Snyder's Director of Photogrpahy..the guy Snyder has worked with like forever...and replaced him.
And the brought in Whedon as a "consultant" on the film ever before Snyder had to leave post production.
And the Marketing and ads for JL are trying to make it look as much like "The Avengers" as possible and and are really stressing the 'Hey guys, this will be a FUN movie"
Fact is the BvS underperformed by what Warners was expecting. They were expecting that the first live action film with The Trinity would do Avengers level numbers, and it did not come close. BvS was a success, but not the level of success that Warners was expecting, and did not give the DCEU the huge left that it needed. Thus the changes at the DC film division, the apparent closer supervision of Snyder on JL,etc,