Study and research, definitely. But I still wouldn’t call it journalism. It’s satire based on research. When going for a joke over necessary details, they will often go for the joke. And if you read the story elsewhere, you will see that something important has been left out because of it.
I love The Daily Show and Last Week Tonight a long with A Closer Look on Seth Myers’ show and I regularly watch all of them, but I still wouldn’t call them journalism. It’s well-researched extremely topical comedy. And that’s fine. That’s a good thing. People can get their information from comedy too. It’s just that you shouldn’t necessarily turn to them for a full picture of a story.
That said, I would say that’s much less true of Last Week Tonight because they go in depth into a subject. The Daily Show and A Closer Look spend at most 6 or 7 minutes on a subject and have to fit in a lot of jokes.