Most of the time, if you are working with money in any form, or in management, companies will run a credit report. A bad credit score can be looked at as not being trustworthy or even as a potential thief. It may not be fair, but unfortunately a lot of companies still use it. Not getting a job years ago motivated me to straighten my credit score out and now it's great and ready for any employer who wants to run a check on it.

This practice is slowly falling out of favor ever since the recession. However, some jobs still require a good credit rating. Mostly banking/insurance/financial advisory roles. No one wants someone providing them advice who can't manage their own financial affairs.

That's been going on for years

I am sorry to hear about this situation. That sounds really unfair and unethical.