Many factors have been given for this, from the fact that Star Wars: The Last Jedi had only been released six months previously to trepidation from fans due to the fact that Lucasfilm changed directors in the middle of filming.
The film just didn’t seem to drum up the sort of enthusiasm that we usually see with Star Wars.
Paul Bettany certainly isn’t alone in his feelings toward Solo: A Star Wars Story as a lot of people did love it, but certainly he does seem to be in the minority.