Of all the deities in the Greek Pantheon, Hera and Zeus stood supreme. They were parents of all. There was none more powerful, more absolute, more untouchable. The only divine being able to thwart either of them was each other.
With Zeus unwilling to take on Hera, there was little that Lamia could do. She was supposed to simply crawl into a hole somewhere, then spend her eternal life regretting ever having taken the Mother Goddess's man. She didn't. She attacked in the only way open to her. She went after the faith in Hera Herself.
New mothers prayed to Hera. She was the Great Mother. Those wishing to become pregnant left offerings for Her too. Older mothers watching their children grow into adulthood still turned to Hera. She could protect their babies. She was not just a mother, but The Mother.
So Lamia killed the babies. All those grieving mothers had placed their trust in Hera, now the cradle was empty. Where was Hera then? Moreover, who had sent this horror into their midst? It was Hera.
Relentlessly, immortally, the insane Lamia preyed upon the nurseries. She took her sustenance from the bodies, blood or life-force of the infants; she took her revenge by eroding human belief in Hera's greatness.
And who won in the end? While classical scholars and Pagans may know all about Hera, it's vampires who survived the centuries to take over popular culture. The legends have changed and the focus had shifted, but the fact of the blood-suckers remains. Lamia's children haunt our literature and movie screens, while Hera is nowhere to be seen.