Even if you take Mazzula's comments as being somewhat reasonable, they are only reasonable when things first start going wrong. Then a coach has to intercede and fix them. He has to see the defense isn't right, figure out what is wrong with it, and then correct it.
It can be reasonable to fail to emphasize defense as a first time head coach for the first few weeks / months but it is absolutely ridiculous that he wasn't able to figure out this flaw over the long haul of his first season.