who is to blame for the tragety of Euripides' Hippolytus? Why?

Euripides pins the blame for the tragedy squarely on Hippolytus' hubris in rejecting Aphrodite (rather than on his lack of sympathy for Phaedra or his misogynism), suggesting that the true malevolent force in the play is uncontrollable desire as personified by the vindictive Aphrodite. The disaffected goddess of chastity, Artemis, however, does not try to protect her favourite, as the gods so often do, but rather abandons him at his very moment of death.

Among the themes of the play are: personal desire vs. the standards of society; uncontrolled emotion vs. excessive control; unrequited love; the sacrosanct nature of oaths; hastiness in judgement; and the distasteful character of the gods (as they to give in to pride, vanity, jealousy and anger).

This excerpt was taken from the source-link below. Hope it helps!