This title that Lille won in the French league is a big surprise, in the rank of the title that Leicester won a few years ago in the English Football League.
Obviously PSG was too focused on other topics, Neymar, the Champions League, the coach ... and during that time they lost the French championship.
PSG is not a well-balanced team, because in addition to 2 superstar players, there are also players who are not at the required level, as you noticed in your comment.
For the next season, they definitely have to prepare much better and bring in new players.
Something was even more of a shock to me yesterday, I thought the last time Lille won a league was like 70 years ago, but apparently there was one just in 2010 and before that it was 70 years that true. Lille wasn't really on the map when the league started, everyone was expecting PSG to dominate big time, they were the finalist of champions league last year and didn't have too much change in the team and now obviously it would have been a wise decision to bet on them winning the league this year as well.
Looking at the result it was a tough situation, let's be honest the championship was decided on the very last game so we can't say it was an easy championship for lille neither, the game was also very close as well just a 2-1 win from Lille and it was 2-0 all game, if Angers scored their goal earlier there could have been trouble.
So, it is a very hard fought, very difficult, very tough championship that Lille won and they deserve all the happiness they have. As a non-french person from another nation I am happy to see such an unexpected result, it made the league more fun to watch for me.