Well, if you're going to piss off people with a hiring decision, then you might as well not hire anyone's favorite and piss off everyone equally.
You know, Johnson's background isn't substantially different than Matt Painter's. Like Painter, Johnson played at the school he coached, a real rarity in the Big Ten. Like Painter, Johnson played high school basketball in the same state as his university. Johnson was a better player than Painter.
Painter spent his first two years at small, lower division schools. Then, he spent a combined 7 years as an assistant at two mid-major D1 schools: Eastern and Southern Illinois, the latter as Bruce Webber's assistant. When Webber left for Illinois, Painter was named the head coach but he only spent a year in that job before moving to his alma mater to be Keady's Associate Head Coach (obviously, he was being groomed for the HC job). Keady retired a year later and Painter was named HC.
Johnson has spent about 15 years as an assistant coach (Texas Pan American, Northern Iowa, Nebraska, Minnesota, and Marquette). That's a longer assistant coaching record than Painter and Painter had only one year of HC experience prior to be named as Purdue's HC.