Marseille are much better this season, they started the season impressively, they definitely have the potential to compete for the top of the standings. We certainly don't ignore PSG dominance, but I think Marseille are at least able to put pressure on and make the competition for the Ligue 1 trophy more exciting. Marseille are currently 5 points behind AS Monaco who are currently at the top of the standings, there is still a chance to reduce the points gap in the next matches.
Marseille are stronger and more competitive while PSG are weaker after losing Mbappe and changing their development strategy since in two latest summer transfer seasons. Decreasing quality of PSG at least in this season, will help some clubs in Ligue 1 like Marseille to have better opportunities of competing the league title.
Lille won Ligue 1 title some years ago as a big surprise but if Marseille or any club win Ligue 1 title in this season, it will not be a big shock. Because with strategic changes in PSG, it's expected that their club will have a transitional phase that makes them weaker and can lose Ligue 1 title to other clubs.
With full focus on domestic competition, De Zerbi seems to be able to make Marseille finish in the Champions League zone, expectations have increased since he took over as manager. If Marseille manages to recruit Pogba in the January transfer window, as is rumored, their strength to become a trophy challenger will be even more taken into account.
A high position in Ligue 1 for joining Champions League next season is important for Marseille. It's their first target in this season, and if possible winning Ligue 1 title will be a very good achievement for their club and De Zebri. Success in Marseille will help De Zebri receiving some good offers in big clubs and improving his coach career.