I got divorced in 2019 and didn't file with Turbotax. Now when I'm trying to file as single why does Turbotax keep including his name in the questions?

I am not positive how the online Turbo Tax works, I only use a purchased version on disk but check with Turbo Tax and ask them if there is there a chance he has filed his taxes online with Turbo Tax in 2019 or previous years and that is how Turbo tax got your information attached with his.

The only way your ex-spouse's name would be associated with your tax return is if you used an account name and password he or you used in the past to log in, or if you entered his name in the current return you are completing.

You can use the My Info menu option to see the personal information associated with your tax return and make changes as is needed.