Happens: coaches get promoted take a college job, transfer to a professional outfit, overseas, move, get married, etc and some just don't care for the style & constraint of da so the decision can be mutual.
This early in the season still have plenty to bulid & develop but could be difficult to find a suitable replacement since most are tied up. More typical to see coach changes at the breaks & easier to adjust. Mid way through the fall or spring can be more difficult. Changes can be postive so along as the system & coaches are good things can work out in the long run.