Former Borussia Dortmund star Kevin Grosskreutz has joined a slew of fans of the club by expressing his incomprehension at Jürgen Klopp joining the Red Bull football empire. Klopp won the Bundesliga in 2011 and 2012 as Dortmund coach with Grosskreutz in his squad. He then moved to another traditional European club – Liverpool – where Klopp lifted the Champions League and Premier League. After leaving the Reds at the end of last season to recharge his batteries, it was announced this week that Klopp would become head of global soccer at Red Bull from January. This would make him a top adviser t…