He worked his way up from Scouting Assistant to Tight Ends coach in 3 years for the most successful NFL franchise over the last 10 or so years. When he did make it to position coach his players broke NFL records. Of course they didn't do all that because of him but it's just as silly to assume he had nothing to do with it. If that were the case, then why have a TE coach at all? Just have a vast horde of scouts who can correctly identify talent and two coordinators to draw up game plans. Pretty silly reasoning when you think about it.
Apparently some people noticed he was doing a good job with the Patriot TEs
before the 2011-12 season even started:
LINK
"If you were grading on a youth-to-performance scale, then perhaps the valedictorian of what the late David Halberstam called, "Belichick U," would be precocious Brian Ferentz, son of former Belichick assistant and current University of Iowa head coach Kirk Ferentz. The 27-year-old Ferentz is listed as an offensive assistant coach, but he's the tight ends coach.
Ferentz, aided by tight end/team sage Alge Crumpler, who is six years his senior, has done a remarkable job with rookie tight ends Rob Gronkowski and Aaron Hernandez, two crucial components of the Patriots offense. Gronk set the franchise record for touchdown receptions by a tight end with 10 and has been a bulldozer in the running game. Hernandez, who caught a Patriots rookie tight end record 45 balls this season and added six touchdowns, has improved at reading zone defenses and running precise routes as the season has progressed."
-Boston Globe January, 2011
Don't get me wrong, I'm not guaranteeing success. I'm just saying a guy with this type of career track to this point coming to Iowa to coach would be hailed as a coup if not for the fact he's the HC's son.
Now that I answered your question let me ask you this: other than his last name, what do you not like about the hire?