I don't see anything wrong with that, even in the cutthroat world of college coaching.
As a comparison, my Marine father missed at least a third of my childhood, because of deployments that were for periods of a year, six months, eight months, four months, etc., and even when he was home he was gone for work before I woke up, got home late, and worked most Saturdays. He also was on a ship in the Pacific when my kid brother was born. He made those sacrifices because he loved and believed in his job, but he still has some regret of how much time he missed when we were kids at home.
So I get why Muschamp hit pause on his career. You don't get that time with your kids back. And while all things being equal I'd prefer a new DC hire who wasn't coming off of a gap year, it didn't seem that hard for Greg Robinson to shake off the rust when he had to take over for Manny _iaz in 2013. Our defense wasn't exactly elite that year, but the transformation of our defense when Robinson took over was night and day.
I'd probably prefer that PK have stayed, but what do I know, and I'm sure I'm missing some behind the scenes discussions about why he's departing. In any event, he's gone, and programs lose coordinators all the time for all sorts of reasons. So if we need a new DC, I sure as hell like the Muschamp hire.