The division of the regal authority between two kings must have produced jealousy--and jealousy, faction.

And the power so divided weakened the monarchic energy without adding to the liberties of the people.

A turbulent nobility--rude, haughty mountain chiefs-- made the only part of the community that could benefit by the weakness of the crown, and feuds among themselves prevented their power from becoming the regular and organized authority of a government [128].
Such disorders induced prince and people to desire a reform; the interference of Lycurgus was solicited; his rank and his travels gave him importance; and he had the wisdom to increase it by obtaining from Delphi (the object of the implicit reverence of the Dorians) an oracle in his favour.
Thus called upon and thus encouraged, Lycurgus commenced his task.

I enter not into the discussion whether he framed an entirely new constitution, or whether he restored the spirit of one common to his race and not unfamiliar to Sparta.

Common sense seems to me sufficient to assure us of the latter.