Sounds like you still have access to the old domain. You could add a robot.txt file to tell search engines not to index. You will need to wait for Google to remove the pages.
But during a Core Update no actions are needed by website owners. And one can expect Google to need extra time to process the Robot.txt file. If they return 404s (depends on how you are redirecting) they will be dropped, but Google may check again if the pages exist.
Since you fixed the problem, I'ld expect everything to work out better than before the update. Clearly the bad content is gone.
Volatility during core updates
However, what you are seeing is likely related to the May 2022 core update. As of this post it has caused a lot of volatility in search rankings ... chatter all over the internet but some have been listed here: https://www.seroundtable.com/google-may-2022-broad-core-update-seo-impact-33512.html
During core updates delays in adding pages slows and some volatility is normal. This update seems to be high on volatility for english sites but the update may not have rolls out globally.
When google rolls back an update
If the update does not produce Google's expected results, Google has been known to roll back an update.