No replies here, so I resolved this problem as follows.
I canceled the re-installation #1 where it asked for the root password. It continued and finally showed Workbench, but neither connections worked.
The Windows installer does not pass the "ACID test" (a term from RDBMS) in which a problem makes the product unusable.
I found some clues at StackOverflow
https://stackoverflow.com/questions/6067694/mysql-reinstalled-but-root-password-still-there-and-i-forgot-it
1. Uninstall all MySQL modules.
2. Delete C:\Program Files\MySQL
3. Delete C:\Program Files (x86)\MySQL
4. Delete C:\ProgramData\MySQL (need to show hidden files)
5. Delete from any Users' AppData folders (my W10 did not have this)
6. Reinstall MySQL
When I did that, MySQL install worked as a new install.