Logic points to Lowery being the primary reason our defense improved last season.
I think logic also dictates that Talor Battle had a fairly positive role in Buie's development. Maybe a little McIntosh. The fact that those two guys can scrimmage against the players probably helped all of the guards, especially on offense.
As for the offense in general, several people have made good points above. More than approach, its personnel changes. The main thing of course is the graduation of Audige. That was sort of a known thing - there was widespread anticipation that "Langborg in for Audige" would improve the offense and weaken the defense. That is self-evident.
I would add that with Audige's departure, the guy who thought he was #1A to Buie's #1, the roles of the other guys are more clearly defined and aligned. This year Barnhizer, Berry, Martinelli and Langborg are all better scorers than Audige and Beran were last year, but everybody defers to Buie. Last year, Barnhizer and Martinelli were held back by Beran to some degree. Berry no longer has to play in Audige;s shadow (or compete with Roper for playing time).
So you lose Beran, Roper and Audige. The offense improves. A lot.
I do have to admit I was wrong about Roper. But, I suppose, so was the coach.
I will credit Collins and staff for adding a number of modifications to the "ball screen for Buie" offense we played last year. We've gotten more open looks this year ,no doubt about that.