They're different coalitions and shouldn't be compared. Obama took young people, people with a college degree, wealthy Democrats, and racial minorities. Clinton took young people, people without a college degree, poorer Democrats, and whites.
Meanwhile, Sanders takes young people, people with a college degree, poorer Democrats, and whites. Clinton takes old people, people without a college degree, wealthy Democrats, and minorities. You'll spot this just doesn't match to either bloc from '08.
It's not as simple as an "Obama bloc" and a "Clinton bloc". There are myriad different interest groups in the Democrats and they don't always work together in the same ways. I think your argument here fails right from the get go because you don't seem to understand this.