I'd say there are several things wrong with it. Most important:
a) Biden has been held up as the front runner, the most electable, and the best chance of beating Trump. These numbers indicate he didn't give enough IA voters a warm and fuzzy, as a result, he's cleaning up the rear. That's bad for the democratic establishment.
b) Sanders even with being in DC during the last run up to the caucus was polling heavy in IA like he is in NH. For Pete to be on his heals or slightly ahead of him is a testament of how flawed the caucus system is. He essentially inherited leftover moderate voters because Biden didn't have a strong showing.
c) This momentum only serves to help his political career going forward but hurts the potential nominee who could be reaping the political capital that he's stealing with his time in the spotlight.