Raises some interesting points and certainly worth the (long) read. My guess is there is more than one reason DJK is not getting a tryout in the NFL. Just some that come to mind, in order or priority:
1) The entirety of his interaction with a well-respected college and former NFL coach over five years.
2) Good numbers at the college level but hardly stellar speed, size and talent by NFL standards.
3) The attitude he exhibited on and off the field. NFL staffs view hundreds of hours of game video, read press reports, do checks when evaluating college talent.
4) A much-publicized arrest with multiple counts, including, as the article notes, the incendiary charge of keeping a drug house, at virtually the worst time in his college career when being considered by coaches and GMs for a chance at the next level. It doesn't matter that he pleaded guilty to just one minor charge. The damage was done.
DJK cost himself the opportunity to compete and to receive a big paycheck in the NFL. This is not on Kirk Ferentz.