When the original Ant-Man opened in 2015, it won the box office two weekends in a row.
In addition, a lot of the movies that could have taken box office share away from the microscopic Marvel hero, like Pixels, Terminator: Genisys, or Fantastic Four, generally flopped, making Ant-Man’s road a little easier.
The only real competition that came out during the entire summer of 2015 following Ant-Man was Mission: Impossible – Rogue Nation.
Most of the big movies, like the first Jurassic World and Minions, had been out for a while.