How is this third X clause an expla

How is this third X clause an explanation of what has gone before ? How is the state of alarm of the people, who recall the Peisistratid times, explained by the statement that the incident of Harmodius and Aristogeiton arose out of a love affair(the true facts of which are not generally known and will therefore now be told at greater length) ? Many Thucydidean digressions are introduced by X, and Classen thinks it sufficient explanation to point this out. But X is used only when the digression explains a previous statement or incident; as, for example, the digression on the Athenian rise to power in the Pentecontaetia explains the Spartan fear of further Athenian expasion(1.88-89). Hence the critics who suppose that Thucydides inserted this digression on Harmodius and Aristogeiton purely in order to refute the current version of the story are forced to regard the digression as irrelevant and the use of X as not strictly logical.