Even if PSG didn't put in the effort, even if PSG had important players injured and lost points, they would still become champions because the opponents they have in the league are weak and very unstable. Take, for example, the recent case of Monaco. In the last game, Monaco managed to beat PSG, in a game where Monaco played very well. So I believe people thought that Monaco would easily beat their next opponent because it wasn't as strong as PSG, but Monaco lost. Ligue 1 has unstable teams, and that's why they aren't a big threat to PSG.