The same pair of eagles have likely used that nest for several years. It is always unfortunate to see a nest destroyed because it represents a great deal of time and effort for those eagles. They are very invested in the space, adding new materials each year as they prepare to raise young.
However, it is not always a total loss for the pair if a nest is damaged. Eagles are not actively using their nests throughout the year. Eagles do not sleep in the nest – they perch on branches at night. The only time eagles are actively in the nest in when they are raising young.
In Minnesota, bald eagles are on the nest February through June. Storms during that period are much more dangerous for an eagle family, and young are sometimes lost when a nest is damaged before they have fledged. But, once the young have fledged, or left the nest, the adults do not use the nest. Both juvenile and adult eagles are spending time hunting and learning to hunt.
The other good news is that the adult pair is very likely to rebuild the nest close by. If the same tree has any viable portion remaining, they may rebuild there. If not, they are likely to choose a place fairly close by. The nest represents a territory to which they are very attached, and have worked hard to defend. They will look for another suitable location within the territory so they can continue to rear young in the area that they know and has been successful in the past.