We saw the same thing happen in professional (American) football. Coaches today wear sweats and windbreakers with their team's logo on it but prior to about 1975, most coaches dressed like they were working in an office. I'm thinking of Vince Lombardi, Hank Stram, Tom Landry and Dan Reeves among others. They all wore jackets with a dress shirt. Even John Madden who frequently appeared in short sleeves, at least wore a collared shirt. But today most NFL coaches wear athletic gear. New England Patriots head coach Bill Belichick wears a sweatshirt with cut-off sleeves. Redskins' Mike Shanahan wears a Washington Redskins windbreaker with maroon pants, turf shoes, etc.
But college basketball hasn't deviated from the semi-formal dress code--at least not until Bob Huggins started going casual. I won't say that it's good or bad, only that it is. My prediction is that this trend will catch on and we will start to see basketball coach fashion trend toward the casual-athletic and away from the Sunday best just as it happened in professional football.