Alex Ratner was trying to get in a few hours of work after putting his kids to bed when news broke that Meta Platforms Inc. planned to invest billions of dollars in data-labeling startup Scale AI. Within minutes, Ratner, who runs a rival company called Snorkel AI, began fielding calls from his board about the chance to pick up clients worried about Scale’s independence.Then came the inquiries from possible customers — dozens of them, he said, resulting in “tens of millions of dollars” in potenti...