When X Corp. chief executive Linda Yaccarino gathered advertisers in September at the company’s New York office, hoping to woo them back to the social-media platform, she invited a National Football League executive as a headline speaker.

Having heard plenty about the risks of the platform formerly known as Twitter, from hate speech to misinformation, Yaccarino and her team have been pitching advertisers on TV-style content such as NFL game highlights—safe zones within X that can give jittery marketers a place to spend their money.