In summary: this year there is a smaller difference between the #1 and #22 ranked teams than last year's #1 and #10 ranked teams. Last year Michigan State made the Final Four as the #15 ranked team in the Kenpom rankings and were legitimate title contenders. The difference between them and #1 Kentucky was 0.0856. If we apply the same threshold this year to determine legitimate title contenders, that easily includes any team ranked in the top 25.
This year's race is wide open, which is why so many teams that make it to the top 5 don't last there very long. Hopefully Iowa can buck this trend.