I doubt any team would purposely score goals against themselves as it is quite obvious and the team would be disqualified. But it is not impossible that they would purposely lose by simply not playing at their full potential, either to avoid strong teams or not to put too much stress on the players if they know they are already qualified.

It is also possible that the strongest teams would "select" which group they are affected to rather than being randomly dispatched (they have to be put in 8 different groups anyway) as [Michel Platini confessed recently][1] about the 1998 world cup (article in french).


  [1]: https://www.eurosport.fr/football/coupe-du-monde/2018/video-platini-avoue-une-petite-magouille-en-1998-pour-que-la-france-et-le-bresil-sevitent_sto6760367/story.shtml