This was exactly what I've been saying.Here is Cobb again talking about what the offense can do different when O'Brien was still the HC.
"Cobb explained that some of the concepts the offense currently utilizes entail more of a “down-the-field kind of ‘shot’ mentality.” He recognized that this becomes “a little bit harder if we can’t hold up up front to be able to make some of those plays happen down the field.” (In other words, ask the offensive line.)
And so the focus may need to be breaking off short routes when teams blitz, in the hopes go giving Watson a target more quickly, especially when he’s being blitzed."
Too many long developing plays (in the first three games) that require the Oline to hold and they're not good enough for that.
They needed more shorter route combos, quick hitting plays (which we saw more of in the last game).