Mike Krzyzewski , Duke Program Suspend Duke Junior Grayson Allen Indefinitely

On Wednesday night the recurrence  of Grayson Allen tripping  opponents happened yet again  at the Greensboro Collesium in the first half against Elon.

Grayson Allen tripped Steven Stanta Ana. This time he is paying the price for his actions. Grayson Allen is suspended for an Indefinite amount of time. "According to http://www.dukebasketballreport.com/2016/12/22/14051832/grayson-suspended-indefinitely-duke-basketball-tripping

Grayson Allen did take an important step in apologizing to Steven Stanta Ana and Elon head coach Matt Matheny 'According to http://www.dukebasketballreport.com/2016/12/22/14051832/grayson-suspended-indefinitely-duke-basketball-tripping

A season ago Grayson Allen tripped two players playing for the opposing teams. He tripped Florida State's Xavier Mayes and Louisville's Raymond Spaulding. Why didn't Mike Krzyzewski and the Duke program take action  then and suspend Grayson Allen ?