This copy of the Install macOS Big Sur application is damaged, and can‘t be used to install macOS.

Drag and Drop the new Application in Applications folder " Install Big Sur " to the trash. Empty the trash and this time shutdown the computer. Move as close the Router as possible. Disconnect ALL Other devices using the Wifi - want the Maximum Bandwidth dedicated to this computer. Restart and Immediately hold the Shift - key. This is Safe Mode and does a repair Disk, clears Cache files and only loads Apple Software so loads slowly - Normal. It will look and perform differently - Normal. Open Apple Apps Store and download the Full Installer of Big Sur again.

Shutdown the computer by whatever means necessary including via Power Button. Disconnect all external drives. Restart and Immediately hold the SHIFT key until the Apple Logo appears.

This is Safe Mode and it will attempt to do a Repair Disk, clear cache files and only load Apple Software, extensions and fonts. It will load slowly - normal. Once logged in, the computer will look and perform differently - also normal. Now Drag and Drop the Install Big Sur to Trash and empty the trash.

unable to drag the application to the bin and thrash