The counterargument is that Obama did do better than expected in some primary (non-caucus) states.
But, the counter-counterargument is that Obama did better than expected in the Southern states, where a plurality of Democrats are black.
He did better in the south from what I remember. Not because he was so strong there either. Blacks in the Democratic primary make up a huge percentage of the voting block. Secondly, Hillary had no game plan in those states (i.e Mississippi) and didn’t have a natural base there