According to the install log, it's only failing to install Formit, but because the installer is so badly designed, it decides that the whole installation isn't worth anything if you can't have Formit and then strips all the software it has already successfully installed off your PC... that's what Rollback means:


So just try the Formit install first and see if that fails too and what the error is...
You might need to run the Microsoft Uninstall Tool first to get rid of any corrupt installations of the software first. Download the program, run it, choose "Problems uninstalling", then see if Autodesk Formit or Autodesk Revit 2020 appear on the list. If they do, use the program to uninstall them (it can only do one at a time, so you might need to run it twice). Clear the temporary files on your PC. Then try the Formit install first, if it succeeds, try the Revit install again. And remember to RUN AS ADMINISTRATOR
Edit: I have no idea why my reply is so weirdly formatted or why it says I'm responsing to myself since I clicked on reply to @Anonymous...