I don't know why that happened but if you have access to another machine, you can create and boot up with a Hiren's Boot Disk.
https://www.techspot.com/downloads/6966-hirens-bootcd.htmlnIf you need to create a bootable USB, this article explains that -
https://www.hiren.info/pages/bootcd-on-usb-diskUse the 15.2 download, but if that doesn't get you back up then try the PE 1.0.1.
I've used 15.2 to get my Win 10 back up but it was on an earlier version than 20H2.
If either gets you back up then I would advise performing a chkdsk /r
You can read the log in Event Viewer.
When it has read the data, expand Windows Logs - click on Application/Action/Find and type chkdsk into the Find box and press Enter.
Cancel the Find box and read the log in the scrollable pane below.
Primarily you are looking to see if it reports any KBs in bad sectors.
If it does then it's advisable to immediately create a system image onto external media in preparation for complete HDD failure.
If the HDD is okay then enter these cmds to see what they report.
dism /online /cleanup-image /restorehealth
sfc /scannow
Enter exit to close the Command Prompt/Powershell window