When Izzo became MSU's head coach, Michigan was the top basketball program in the state and one of the most successful in the country.
The break (from Izzo's standpoint) was Mateen Cleaves' official visit to Michigan. His Michigan hosts decided to take a road trip, which isn't allowed on official visits. On the trip, they athletes got into a rollover accident in Robert Traylor's rather well accessorized SUV.
Because of the visit violation, Michigan had to stop recruiting Cleaves; and because of the expensive vehicle Traylor was driving, the NCAA began to look into Michigan's program. Izzo seized the moment by signing Cleaves, thus solidifying the Flint pipeline. Flint's Morris Peterson was a year ahead of Cleaves, and Charlie Bell followed to form the core of Izzo's 2000 National Championship team. From that point forward, Izzo beat Michigan for the lion's share of in-state talent. The Michigan investigation dragged on for six years thanks to the former players' stonewalling (they hadn't paid taxes on the money Ed Martin gave them and therefore didn't want to cooperate), and the prolonged threat of probation (followed by actual probation) inhibited UM's recruiting more each year.
Izzo is a great coach. It isn't far fetched to believe he would have had the same success without Michigan's dishonesty being exposed although it might have taken a few years longer to get to the top. Nevertheless, Michigan's fall opened the door for MSU's rise, and Izzo made the most of it.