PSG, who risk losing Mbappe for free when his current deal expires next summer, rejected Real Madrid’s bid of around €160m for the 22-year-old, deeming the offer too low.
“The fact that he’s staying, that was the only thing that could happen,” Leonard told Canal Plus.
“We never thought about doing all this without Kylian. We were not happy with the behaviour of Real Madrid.
“We were clear about the offer they made. It was not enough from our point of view. It was less than what we paid.
“As for their last offer, it never arrived.”
Mbappe has been in great form this season, scoring four goals in six games, and is expected to start Wednesday’s Champions League game at Club Brugge alongside Lionel Messi and Neymar.
“I don’t see Kylian leaving at the end of this season,” said Leonardo.
“Mbappe’s relationship with PSG is deep. I don’t think anyone here sees the future without him.”