A more apt comparison might be pastoralist raiders as mentioned in Turchin's War and Peace and War, whose nomadic lifestyle led naturally to the development of military skills that could be applied in raids on settled communities. Turchin wrote a lot about the Tatars and the Mongols could also be a good example.
Their empire was, of course, extremely short, as it collapsed with the death of their Great Kahn soon after it established itself and its following leaders abandoned the previous inroads in the West to focus on the prize of capturing China (that ultimately failed).
Our history tends to focus on the expansion of their empire rather than its subsequent administration, I think in part for that reason.
IMO, all empires are small compared to the Mongols. They had it all.
The Danes just had lousy farmland and good boats, especially during long cold spells. The Northmen in general had more impact as traders than as raiders.
A similar pattern emerges in the Americas - the Apache word for the Comanche is Apache for "those a$$holes" because the Comanche were much more predatory of the Apache than the other way 'round.
Remember the story of the Danes was told by the recipients of their raids, who had an interest from a religious standpoint to portray them as awful pagans.
A tribe of pillagers could destroy a hamlet, but could never compete with the resources of a walled down.