Windows 10 ISO download for Bootcamp fails repeatedly

I am trying to install Windows 10 on my 2012 MacBook Pro using Bootcamp and a 32GB USB thumbdrive that has been formatted according to the Bootcamp instructions as MS-DOS(FAT) and Master Boot Record but for 3 consecutive tries, ISO download fails due to file being too large, even though it shows as being a 5GB file download. I also tried reformatting only the partition as above, tried formatting the master volume as above, but same result: failed download of the ISO file. When I tried downloading the ISO file to the same thumb drive formatted as MacOS Extended Journaled, the download completed but the drive was unreadable by Bootcamp.

Also, my macOS version is 11.5 Big Sur and I ran Software Update before attempting the download of the Windows ISO file.

Any ideas as to what I am doing wrong?

Thanks!