Ancelotti departed PSG to take charge of Madrid in the summer having won the Ligue 1 title with the French club last season.
"We didn't have a real identity to our play in that first season," he told the official Ligue 1 website.
"That wasn't true of the second season, especially the second half of the second season. In the Champions League we only narrowly lost out to Barcelona. I felt respected in France; it was just difficult to change the working mentality when I arrived.
"We needed to change that in order to fulfil the ambitious objectives set out by the Qataris (Qatar Investment Authority, owners of the club), in order that Paris became a team in accordance with the financial potential of the club. I think Paris has improved a lot on this front and now PSG has that winning mentality."
PSG were beaten in the quarter-finals of the Champions League by Chelsea this season.