After a shaky start, Inter now sit top of the Serie A table under rookie coach Cristian Chivu.
Marotta said at a college Q&A: "I'm surprised people were surprised by Cristian's ability.
"We chose him because he represents important values; he had the courage to go against the grain, even in the media.
"Some even mentioned (Jose) Mourinho who, with all due respect... If I hadn't had the courage, I would have regretted it."
He also stated: "The equation is no longer 'if I spend, I win,' but rather motivation must be multiplied by competence.
"And that's what the French (PSG) have done, changing their role model: no more big names, let's invest in young talent."