What do you think?
I see it the same way like you. I think not cloths should matter (it's not a fashion show!) but the performance on the chess board (especially as jeans are something completely normal to wear).
A really ridiculous decision in my eyes.
There was something about fairness in the fide statement:
"FIDE regulations for the World Rapid and Blitz Chess Championships, including the dress code, are designed to ensure professionalism and fairness for all participants."
Maybe one of the opponents complained that he only lost to Magnus Carlssen because he was wearing jeans.