In this case it is because the posting account has explicitly ticked 'Ask apps and sites not to show my account to logged-out users'. Of course, Bluesky is built upon the open AT Protocol, so you can still view the post by any one of a number of other means without requiring a complex workaround.
He has spent the last few months repeatedly posting the same comment about hitler being a socialist. If it was just the salute in isolation it could be questionable, but now there is no doubt.
