I let my toxic manager get fired for a massive database mistake that I actually made

My old department manager was the kind of person who took credit for every successful project and publicly humiliated subordinates whenever anything went wrong. he was also extremely lazy. To avoid working late, he gave me his personal master login credentials so I could handle late-night client updates and system imports from my desk. About nine months ago, I was working exhausted at 1 AM and accidentally overwrote an active client database with an unverified backup script. It corrupted two weeks of live transactional records and caused a massive panic across upper management. When the internal security audit pulled the logs the next morning, everything pointed directly to his master admin account. Instead of owning up to giving me his password, he panicked and lied to the directors. He claimed his account was hacked from an outside source. Management brought in IT, found no external breach, and decided he was covering up his own incompetence. They fired him by Friday afternoon for gross negligence and data mismanagement. I sat in my cubicle with my mouth shut the ENTIRE time. Two weeks later, they promoted me to interim lead because I was the only one who knew how to restore the database. The office has been peaceful ever since he left, but every time I log into that system, my stomach twists into knots.