but what that money was used to get in terms of favours. It undermines the entire system.

Absolutely. Tigers and Flies wasn't just about restoring public trust, it was started soon after the neutralization of dozens of CIA sources, who had been uncovered with the help of Iran's own counter-espionage. Before the campaign, corruption allowed for the CIA to effectively pay-to-win in the 90s/00s - they could simply bribe officials to promote assets into more powerful positions.