Neymar is a really great player, as is Mbappe, but their vanities are huge and it is obvious that the PSG team can't have two leaders.
PSG tried to elegantly solve this problem and get rid of Neymar, but they failed because other clubs know very well what they get with Neymar, as an additional package.
PSG has a great and very expensive team, but if they don't solve the problem between Mbappe and Neymar, they won't fulfill their main goal again, winning the Champions League.
I would not call this a problem between Neymar and Mbappe (although formally it is), the main problem is Mbappe, who fell ill with star disease and requires special attitude and additional privileges. PSG bosses themselves are to blame for this situation, since in any top club (and especially in such a money bag as PSG) there will always be more than 1 star, which means you need to select players so that they can work together without conflict.
That's right, many PSG fans also regret the attitude shown by Mbappe. conflicts with some players will certainly make the team's performance will be problematic when all of them are played as starters.
even with a team full of stars. when they clash, of course, it won't make the team fine. although it was facing a not-so-strong team. coaches and club management must immediately address it. otherwise, the club will be really at a disadvantage. even they have to forget the dream of the UCL trophy this season.