This isn't always the case. There's always a lot of talk in college football when a team changes offense/defense and there's a perception that it takes them time to adjust. In many cases that team ends up having a leg up on the competition though because there's no previous game film to scout them, especially early in the season. We saw when Weis came in the offense was clicking on day 1, and gradually teams began to scheme against us better and better as the season went on and as Weis' time in South Bend drew to a close. Similarly when Elko came in our defense played very well early, and we gave up more points as the season went on. You can see it in other programs too, like how Urban Meyer was able to step into his Florida and tOSU jobs and be successful early on despite adjusting the team to a very different scheme.
There are certainly exceptions, but I think it's very much a common misconception that teams struggle to find footing after switching schemes. You have to remember when a team has faced the same Pro style offense run by a coordinator year after year, it can be more difficult for that opposing team to game plan when a new coach comes in and switches to say...a Spread offense. There's just a lack of game film and situational experience facing that coordinator, so you have less data and analysis to work with.
