1. It has long been the tradition, that even if the protagonist and the antagonist have the same amount of screentimes, the protagonist would still get prioritised in the credits order, except in some cases where the actor playing the antagonist is a much bigger draw, e.g., Nicholson.

2. Ridley has boomed quite a lot bigger than Driver. She's been much more at the centre of attentions since Awakens compared to her other young co-stars, and she has proved to be more popular among the fans as well, getting plenty of more votes in fandom awards and whatnot.

3. In terms of box office draw. Driver had a major role in Logan Lucky, which recieved excellent reviews and was a comedy heist film, which is quite an audience friendly genre, playing alongside Craig and Tatum, who are both draws (Not to mention McFarlane), and the film still flopped despite the small budget.

Ridley made an appearance in Orient Express, a mystery drama, that received mixed reviews, and she shared the screen with only two other major stars, Cruz, who hasn't been in the spotlight for quite a while, and the box office poison known as Johnny Depp, and the film still ended up doing a heck of a lot better than Logan Lucky and became a huge success.

There really is no justification for Driver's name to be mentioned before Ridley in Jedi's credits other than gender bias.£