McBride (from his conversations with Parella) says that Diaco was often teaching the kids by himself while the other assistants watched because of the lack of trust among the coaches (implying Diaco wouldn't let the assistants coach). Also Diaco had them just learning exactly what to do each play and not learning why, which led to things like the DL only bull rushing and not having a repetoire of moves and techniques. And there was no individual time scheduled for practicing fundamentals. All of which led to the players being confused and thinking too much and worrying about making mistakes.
Basically Diaco was a sh!tshow and also mentioned that Riley didn't seem to want to fix things.