I dont think anyone had any clue what would happen with the eggs would happen that way. From the way I understood it, the dragon eggs were very rare, since it had been 1k years since a dragon was even seen. So these fossilzed eggs were something like a giant gold nugget. They were valuable because they were rare.
It was not until the witch doctor killed off drogo and the stallion that would mount the earth, and khaleesi not burning her hand that she kind of put two and two together, IMO. An completely unexpected turnabout.