In regard to the significance of the change of administration in the world of gods, Saxo ( Grammaticus) has preserved a tradition which is of no small interest. The circumstance that Odin and his sons had to surrender the reign of the world did not imply that mankind should abandon their faith in the old gods and accept a new religion. Previously the Aesir and Vanir had been worshipped incommon. Now, when Odin was deposed, his name, honored by the nations, was not to be obliterated. 
The name was given to Ull, and, as if he really were Odin, he was to receive thesacrifices and prayers that formerly had been addressed to the banished one (Hist., Book 3). 
The ancient faith was to be maintained, and the shift involved nothing but the person; there was no change of religion.
 But in connection with this information, we also learn, from another statement in Saxo, that the myth concerning the war between Aesir and Vanir was connected with traditions concerning a conflict between various views among the believers in the Germanic religion concerning offerings and prayers.
 The one view was more ritual, and demanded more attention paid to sacrifices. This view seems to have gotten the upper hand after the banishment of Odin. It was claimed that sacrifices and hymns addressed at the same time to several or all of the gods, did not have the efficacy of pacifying and reconciling angry deities, but that a separate sacrificial service should be given to each one of the gods (Saxo, Hist., Book 1). The result of this was, of course, an increase of sacrifices and a more highly-developed ritual, which from its very nature might have produced the same hierarchy among the Teutons as resulted from an excess of sacrifices among their Indo-European-Asiatic kinsmen. The correctness of Saxo's statement is fully confirmed by strophe 145 in Hávamál, which advocates the opposite and incomparably more moderate view in regard to sacrifices. 
This view came, according to the strophe, from Odin's own lips. He is made to proclaim it to the people after his return to his ancient power.
Betra er óbeðiðen sé ofblótið,ey sér til gildis gjöf; betra er ósenten sé ofsóið.Svo Þundur um reist fyr þjóða rök,þar hann upp um reis, er hann aftur um kom.
Not to pray is betterthan to over sacrifice,A gift always seeks recompense; Not to sacrifice is betterthan to over immolate.So grave Þundurbefore the history of man,where he rose up,when he came back.

The expression, þar hann upp um reis, er hann aftur um kom, refers to the fact that Odin had for some time been deposed from the administration of the world, but had returned, and that he the proclaimed to the people the view in regard to the real value of prayers and sacrifices which is laid down in the strophe. 
Therefore it follows that before Odin returned to his throne, another more exacting doctrine in regard to sacrifices had, according to the myth, secured prevalence. This is precisely what Saxo tells us. It is difficult to repress the question whether a historical reminiscence is not concealed in these statements. May it not be the record of conflicting views within the Germanic religion - views represented in the myth by the Vanir on the one side and the Aesir on the other? 
The Vana views, I take it, represented tendencies which, had they been victorious, would have resulted in hierarchy, while the Asa doctrine represented the tendencies of the believers in the time-honored Indo-European custom of those who maintained the priestly authority of the father of the family, and who defended the efficacy of the simple hymns and sacrifices which from time out of mind had been addressed to several or all of the gods in common. That the question really has existed among the Germanic peoples, at least as a subject for reflection, spontaneously suggests itself in the myth alluded to above. 
This myth has discussed the question, and decided it in precisely the same manner as history has decided it among the Germanic races, among whom priestcraft and ritualism have held a far less important position than among their western kinsmen, the Celts, and their eastern kinsmen, the Iranians and Indians. That prayers on account of their length, or sacrifices on account of their abundance, should give evidence of greater piety and fear of God, and should be able to secure a more ready hearing, is a doctrine which Odin himself rejects in the strophe cited above. He understands human nature, and knows that when a man brings abundant sacrifices he has the selfish purpose in view of prevailing on the gods to give a more abundant reward - a purpose prompted by selfishness, not by piety.

- Viktor Rydberg “ Investigations on Teutonic Mythology”Chapter 37

The Aesir Against The Vanir” by Carl Ehrenberg (1882)