It makes sense that Trump is invoking Bobby Knight here. Knight met the main criteria to be spoken of favorably by Trump: he supported Trump in the 2016 election.

Bobby Knight was a one of the all-time great college basketball coaches. He was a genius. He also valued academics, and as I recall all of his teams had a high graduation rate. But he said stupid shit all the time and was verbally (and physically) abusive to his players (and everyone else, even his friends). He once was so upset at a call fhat he threw a chair on the court during a game. There is a litany of other abuses o his wiki page, but this one stands out for me, because it was just a passing comment that sheds some light on how he thought:

In an April 1988 interview with Connie Chung, when discusssing an Indiana basketball game in which he felt the referees were making poor calls against the Hoosiers, Knight said, "I think that if rape is inevitable, relax and enjoy it." In response, women's groups nationwide were outraged by Knight's comments.

Bobby Knight is the perfect example of a leader from the 70s and 80s whose personality simply wouldn't be tolerated today without major changes in their philosophy. I bet Donald Trump thinks that it's a shame that his life is controversial at all, but he is just one of a long line of abusive people who got a pass because they were perceived as tough leaders.