With the accession of Aelle to the position of “overlord” (for lack of a better word) of the Germanic lands in Britain, the idea of an overall leader of disparate tribes had infected the Germanic tribes as well.
Britain, it will be recalled, had had High-Kings for decades. Vortigern is generally believed to have been the first to be verified as High-King of Britain. Following in his footsteps were Uther Pendragon and Arthur. Faced with an onslaught of Saxon invasions/migrations, the Britons rallied round the flag of one man, who united them in army and purpose and then pointed them in the right direction–against the common foe.
Britain in the 5th century was still a patchwork of traditions. Yes, the Romans had done their level best to Romanize Britain, but the stubborn Britons had clung to their traditions, their religions, and their beliefs. When the Romans rudely departed, the disparate tribes were left to fend for themselves. In the idea of a High-King, they found solidarity. In the reality of a High-King, they found solidity of purpose. The ruler wasn’t all-powerful, as some of his successors. (King John comes to mind.) But he did speak for a majority of the Britons, who saw their futures to be one commonality and their enemy to be one and the same–the Saxons. It was all very well and good to argue over whether which neighboring town had the fiercest fighters, but it was another thing entirely to put centuries-old conflicts aside and stand arms-to-arms against a foe that threatened their way of life.
The Saxons learned this lesson, too, starting with Aelle. (It could very well be that he learned by watching his enemies.) As Sussex grew and other Germanic settlements sprang up, the same sort of patchwork that had enveloped both Briton and the Continental homelands settled onto the Germanic settlements in Britain. Saxons had different priorities than did Angles and Jutes. South Saxons had different goals than did West Saxons. The triumph of Aelle came in his ability to rise above the petty concerns of his Germanic brethren and unite the people in a common cause–the colonization of their new homeland. It was an ironic twist of fate that the peoples that would make their new home a “nation of shopkeepers” would learn the tricks of the trade from their enemies.