In football there are sometimes that loses are bound to happen and despite the fact that PSG lost that game go Chelsea doesn't necessarily mean that they will be lose in their game in league 1 because with the quality and standard of that team I don't think any other team can actually challenge them for the league 1 title because they will be winners at the end of the season again and besides lille and Monaco aren't actually big team to give PSG headache.
Club world cup tournament is not such that you can compare the Ligue 1 with, that is a way too big tournament than the league 1. PSG do not face as much challenge in Ligue 1 like they did at the club world cup. So they are very likely to do even much better in Ligue 1 because it is less challenging as compared to top leagues like the champions league, europa and the club world cup tournament. Besides Lille and Monaco like you mentioned Marseille is another team that is supposed to be a challenge to PSG in the Ligue 1 but they still have not found a solid form upon which they will build strength for such challenge.