It starts as a culture issue, then becomes a confidence issue. From my own coaching experience, once otherwise good players lose confidence in a part of their team, they try to make too many plays on their own, take too many chances, and end up blowing assignments and getting burned. Dominoes from there. You could see that last year--it seemed that once we gave up a couple of touchdowns, the opposing offense would just snowball.
I trust Bronco can fix the culture issue, although he should never have allowed it to exist. What does a player say when culture suddenly changes around them ? They talk about "buy in"...