The answer is: make fun of the subject
The satire that was made by Juvenal made fun a lot of people (including those who had high power) in roman society.
Satires such as The Emperor’s Fish , or True Nobility made fun a lot of fake bravado and charisma that people in high power tried to impose at the time. Since he wrote it in such a funny way, many people who read it could easily relate to his opinion and made him really popular.