Why is Hector a very important character in this story?

Heartbreak House by George Bernard Shaw is a play criticizing the British upper classes of the Edwardian era. Shaw explicitly draws parallels between this play and Checkov's analysis of the decline of the Russian aristocracy. It also draws upon Matthew Arnold's distinction between the barbarians (Ariadne Utterword and "horseback hall") and philistines ("heartbreak house"). All of the major characters in the play are important exemplars of certain social and psychological types Shaw sees as typical of the period and milieu.
Hector Hushabye is important to the plot of the play in several ways. First, he is the husband of Hesione. He has a vivid romantic imagination and fantasizes about a more glamorous, adventurous life, but in reality lives a life of comfortable and unadventurous domesticity. In the central plot concerning Ellie Dunn's maturation and growth in wisdom, Hector is a love interest. Ellie has met him before the time of the play's action, when Hector pretended to be a mysterious figure called Marcus Darnley. Ellie had a crush on Marcus, but is disillusioned when she discovers that Marcus is really Hector, and he is not actually the romantic adventurer he pretended to be. He is an important example of how Shaw sees the upper classes as presenting a false and ultimately unsustainable facade to the public.