Why Danish kings seek to gain neighbouring realms and, after these have been acquired, very soon lose them

SAXO observes that when St Canute contemplated extending his king dom of Denmark, he recalled that nothing had more amply increased the warlike glory of his forbears, together with the wealth of their dominions and the breadth of their territories, than their claim to England, and they had attained greater splendour from the spoils of this one island than from the whole of Russia to the east.