He's the director of the Center for Child Health, Behavior and Development at Seattle Children's Research Institute, and a professor at the School of Medicine of the University of Washington, who has published over 170 research articles and also a pediatrics textbook, and whose research has focused on how early experiences impact children and their learning environments [1]. That seems like it should qualify him to offer a meaningful opinion on the topic at hand.

OK, to be fair, they didn't mention all that in the Times article, but they did mention that he is the lead author of the American Academy of Pediatrics's guidelines on screen time. As far as I am aware, the AAP has a good scientific reputation, so one would expect that they wouldn't get someone who doesn't know his stuff to author their guidelines.

The Times also has a good reputation, so I'd expect the journalist to have looked up Dr. Christakis and seen that he appears to be qualified on this subject.

You are right that we shouldn't unthinkingly trust...but we also to avoid being excessive about it, because no one has the time to personally check everything. This is why reputation matters. If you get your information from reputable sources, you can delegate more of the checking to them without much risk. This is one of those cases, especially since they gave enough information to trivial look up more about him if you don't want to go by the Times and the AAP reputations.

[1] https://www.seattlechildrens.org/directory/dimitri-a-christa...