To be sure, the changes in the legal market from 2008 on reduced the opportunities for BYU grads to go to big law. It affected everybody, but BYU's in-roads to BigLaw were probably more susceptible to reduction than other, more established, schools.
But I don't buy the "LDS Attorneys Bail" angle. The irony of BigLaw is EVERYBODY bails. And, even though they say otherwise, BigLaw expects - even wants - associates to churn. It's the business model.