It seems that Marseille has a better effort to stay below PSG in the Ligue 1 standings this season, because Marseille is also the second team with high productivity so far. If Marseille remains consistent with winning every match, then maybe Marseille will have points closer to PSG as time goes by. Because after all, PSG also sometimes only get a draw and could experience an unexpected defeat on another occasion later. Thus, the most important thing for other teams is to succeed in maintaining their consistency if they really want to compete strongly in the trophy fight with PSG this season.
If Olympic Marseille actually had made a better effort to stay behind Paris Saint Germaine like you suggested, they wouldn't have been sitting in the second position of the league table and trailing league leaders with 7 points. Marseille actually started the season on a very good note and I remember telling us that they look like a team that's finally going to give reigning champions a good run for their money but few games into the season, they started dropping points in games they were supposed to win before they recently picked up good form again. You can't be inconsistent and expect to win the league which is why I expect PSG to still retain the French league title at the end of the season