Ok, this may be bro-science, but whenever I see eggs on glass someone always comments "free fish food." I've even said it myself over the years. In reality I have no idea. Surely something will eat them because it's pretty rare to get loads of baby snails in our tanks. It's happened (see next section) but it's far from common. Now that I give it few moment of consideration, something eats them for sure! I've seen crabs and snail swarm an old rotten silverside head that I uncovered once in my tank. It was foul and it got cleaned up pretty quick by the crew.
The most well documented case of a baby snails in the ARC community was from
@Shawn He has since moved but his memory lives on! (He was the best President we've ever had especially compared to the current one) He had a large frag system that had tons of trochus snails in it. Teeny tiny ones, mid sized one all they way up to jumbos. You could pick up a few of the tiny snails and they could access every inch of the aquarium. They were perfect for cleaning frag racks because they were small enough to fit through the plastic squares. The were most abundant is his 40g refugium. Once they hatch, the one's that made it to the refugium were pretty safe from predators. It was great while it lasted because that was a few years ago and trochus snails were pretty hard to come by even at $7.99 ea.