He succeeded his unpopular uncle Huneric, and for that reason alone, enjoyed a rather successful reign.
In accordance with Genseric's laws on succession, which decreed that the oldest member of the family would be the successor, he was proclaimed king.
Gunthamund benefited throughout his reign from the fact that the Vandals' most powerful rivals, the Visigoths, Ostrogoths, and the Byzantine Empire, were all heavily involved in wars.
Although the Vandals' power had fallen off greatly since its zenith under Genseric, they enjoyed peace under Gunthamund.
Unfortunately for the Vandals, Gunthamund died in his mid-forties and thus did not reign for a long time.