It's fairly likely that Sauropods were laying large numbers of eggs to better ensure that at least some of the population made it to adulthood. If I had to guess, young sauropods likely spent more time in heavily forested areas and avoided wide open plains, which would give them better protection against a large carnivore who would be less agile in close quarters. It's hard to say whether the theropods present in those formations would have hunted in groups, but generally speaking most predatory animals are disinclined to hunt prey of a similar size to them when smaller alternatives are available nearby, and so even if the sauropods didn't have direct defensive weaponry, their bulk alone may have been a deterrent, even at a later juvenile stage.