Incredibles 2 starts with all superheroes banned because society has grown tired of cleaning up their messes, and perhaps because people are jealous of their great abilities, as seen at the start of the first The Incredibles movie.
The Deavor siblings launch an effort to rehabilitate the reputation of superheroes and legalize their activities. This effort is successful, but the viewer discovers that the bad-guy,
Evelyn Deavor, actually wants to ban all super-heroes.
Her plan is to help legalize them, and then film them doing something horrible so that they can be banned again.
Why? This seems to be a complex way of doing nothing at all.