I get a laugh out of the no experience laugh - Larry Bird took over an NBA team with zero years of coaching experience and only lead the Pacers to their best ever record at the time and the Eastern Conference finals in 1997. It is a lot harder to coach a group of NBA guys and Bird did it with no experience and succeeded....
I don't think you can really make the case that it is harder to coach a NBA team. There are many, many aspects of NCAA Div 1 coaching that are harder than the pros. One primary aspect is that there is a huge gap between high school ball and college BB, that gap is a chasm when talking about HS and competitive level top level Division 1.
In the NBA:
You can recruit top level experienced players from other teams in trade or free agency. Your players are almost all seasoned professionals. Your players are not full time students. You have as much time as you need in a week to prepare your players. You do not have to make your players top level from truly inexperienced, they have already been developed for you coming out of either other pro teams or after years of college ball. You can recruit using financial incentive as a primary motivator. You do not have your players for only a maximum of four years.
Really, there are lots of challenges in NCAA Div 1 ball that are not encountered in the NBA. In many ways, coaching in NCAA Div 1 is harder and more challenging than coaching in the NBA - not to make light of the difficulty of coaching at the pro level.
Add the fact that FH has no real, substantial NBA coaching experience either, and you have a strange situation where you are handing a Div 1 college program to a former player with no actual coaching experience. (No NCAA recruiting, no player development, no NCAA real-time game strategy experience - normally, that's an Asistant hire at the most, until they gain experience and prove themselves) It will be a great challenge for him to say the least.
Let's hope he gets surrounded with some top level staff. No matter how fast a learner he is, he is going to need some big-time experienced staff to help him come up to speed and to ensure that the weak spots in his resume are not exploited.