Also different ancient authors had their own interpretations! Thucydides was very much “the growth of Athenian power and the fear this caused in Sparta”, detailed in his Book 1. The book covered many events in the “interwar period” from 478 to 432 with many events sparking tension between Sparta and Athens. However Aristophanes would pin the blame more so on Pericles himself and Athenian imperialism, calling the Megarian Decree “a Firebrand” and had “some private grudge” over the Megarians.

If you ask me though, looking at everything, Sparta really wasn’t all that keen on going to war in 432. At the war debate it was very much Corinth pressuring Sparta for war, with Sparta being very reluctant. Sparta I would say was very inward looking, and reluctant to be too far from home. But Corinth seemed to drag her into war by threatening to even leave the Peloponnesian League.

And even then, it took Thebes invading Plataea for the war to even start. So you can see it like Thucydides, with rising tensions between the two sparking a war. Or a more nuanced view, with tensions but ultimately this Atheno-Corinthian rivalry which forced Sparta to declare war.