|This is called "The Espousal" but
I can't decide if they're celebrating
or if he's abducting her. Fitting, really!
image © me!
What if, in part, this was the purpose of Theseus' abduction of Helen in the myths?
The House of Atreus was known to be cursed, after all, and I have no trouble believing that if Theseus made an honest offer of marriage to Tyndareus and it was refused in favor (either in fact, or by assumption) of Menelaus and Mycenae, Athens would find that snub very offensive indeed. How dare Sparta insult their hero by choosing a cursed man as the husband of Helen over Theseus?
But that wouldn't be all. You see, the conflict goes both ways. Say that, in retaliation of this snub, or even just for funsies, Theseus chooses to take what he wants after all. He's deserving. Certainly he is, by pedigree, a better match for Helen than Menelaus could ever be. Theseus is a son of Poseidon, a (for the moment) successful and powerful king, and a hero equal only to Heracles. Add into the equation the dodgy influence of piratical Pirithous, and it's easy to see how Theseus might be persuaded to pursue Helen without her father's consent. Even to go so far as to kidnap her (because it isn't like he hasn't whisked women off before--and that kind of behavior was well established by Heracles, and even more established by the behavior of the gods who did that kind of thing with great regularity. Helen herself is a product of this same entitlement, after all!).
Sparta, taking great offense by the kidnap of their princess and HEIR, sends off their best to get her back. Helen's brothers, Castor and Pollux--the Dioscuri--find her if not in Athens, at the very least, under the power of Theseus, possibly even violated by him! I can't imagine Sparta not being highly insulted and infuriated by such a thing, and these Greeks-- they know how to hold a grudge.
Take into account the fact that in the process of Helen's retrieval, Castor and Pollux upset the inheritance of Athens by giving Menestheus control of the city, and you've got an even greater recipe for long-standing conflict. Sparta has just meddled in Athens' politics and put their man on the throne. You don't even need Athens to have been insulted by the choosing of Menelaus over Theseus first (though I will say that I find that to be pretty compelling).
In this one story, a relative latecomer to the drama and tragedy of Helen of Troy, the seeds of enmity between Sparta and Athens have been sewn. These Myths, after all, are the ancient Greek way of explaining the whys and wherefores.
So, why are Sparta and Athens constantly finding reasons to dispute with one another? Well you see, once long ago, there was a girl named Helen....
Just a thought.