Boot Camp ‘bootable USB drive could not be created’ and ‘EFI system partition formatted as NTFS’

I did a fresh macOS install and wanted to install Windows 10 back but Boot Camp is asking for a USB drive. High Sierra wasn't asking for it as a Windows 10 ISO file was enough. Even if I try to install with a FAT formatted USB drive, I still can not install. I have a default Fusion disk which came with iMac but I’m not using it. I installed a 500 GB SSD.

Video: https://youtu.be/aVuB6MHjnzk

Trying without USB connected. I wasn't asked for a USB when I was on High Sierra on the same computer. I want to install to 500 GB SSD (macOS container):

Trying with a FAT formatted USB disk:

Also tried the way without Boot Camp as described here but with no luck: https://fgimian.github.io/blog/2016/03/12/installing-windows-10-on-a-mac-without-bootcamp/

Windows detected the EFI system partition was formatted as NTFS. Format the EFI system partition as FAT32, and restart the installation. (Screenshot)

$ diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                 Apple_APFS Container disk1         499.9 GB   disk0s2

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +499.9 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume macos                   41.5 GB    disk1s1
   2:                APFS Volume Preboot                 44.3 MB    disk1s2
   3:                APFS Volume Recovery                517.0 MB   disk1s3
   4:                APFS Volume VM                      2.1 GB     disk1s4

/dev/disk2 (internal):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         28.0 GB    disk2
   1:                        EFI EFI                     314.6 MB   disk2s1
   2:                  Apple_HFS apple ssd               27.6 GB    disk2s2

/dev/disk3 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *30.8 GB    disk3
   1:                 DOS_FAT_32 WININSTALL              30.8 GB    disk3s1

I had the same problem. I formatted the disk manually using disk utility to ms-dos first, restarted the bootcamp assistant and it worked.