DUPTIN!  For a three-part blog series about the causes and effects of the IRS "first to file" policy, click here:

https://procedurallytaxing.com/duptin-part-iii/

And you are jumping to conclusions by accusing the ex-husband of being the one who got there first.  It could have been last year's preparer, or a neighbor of the taxpayer who found the SSN in the trash.  IRS never identifies the other claimant.