PSG wants to focus on the Champions League and try to get the title in this tournament but they are not alone. Teams like Real Madrid also want the same thing but it was also hard for PSG to have any achievement in this tournament. Now PSG's first priority is the Champions League because they know winning the French League 1 is not hard for them considering the money they have spent on this team.
Currently, the only team they have raced with PSG is Marseille because of the good performance we saw from them but even Marseille is not strong enough to make any problem for them yet.
It's not new that PSG want to win Champions League as they invested so much money through past years and only had one Champions League with a defeat under Bayern Munich. They want to have other Champions League final matches and want to win it for a first time, to make a milestone for their club, then will continue with more titles.
Ligue 1 is a domestic league where they have to play to get a ticket to Champions League, and they will have to continue fighting there, but winning titles in Ligue 1 is no longer interesting with PSG. They are still very strong in France and can continue their domination in Ligue 1 but by lack of focus on the league, other French clubs can have opportunity to take over the title from PSG, if they are strong enough to take advantage of PSG carelessness. So far, French clubs are not ready to beat PSG and PSG will win more Ligue 1 titles like Bayern Munich in Bundesliga.