It's a very difficult choice for mbappe right now. It's caused by PSG is not willing its player to dictate the club.
I hope that PSG will sell him as soon as possible. Im sure that manchester united will be sending a huge offer to the PSG for him.
IMO, Mbappe really needed by manchester united as his skills to play in the multiple roles very helpful to the club.
Mbappe does not dictate anything, he just told the management about his decision and they have to make a decision. They do not want to let him go as a free agent, because they understand that a lot of money was spent on transfers and salaries, but PSG did not achieve their goal, so they want to return at least some money. They want assurance that Mbappe won't leave and obviously the team needs him, but apparently Mbappe wants to play for other clubs while he's young and full of energy.