"
Que" here, is an emphasis on the statement "(but) we are more". In context: "
We are more than anyone would have expected".
In Spanish from Spain this kind of sentence always starts with "que". In Mexico we would have just said "somos más, ¿eh?"; if an emphasis was needed, it most probably would have been made with exclamation marks.
We only say "que somos más" when we are repeating the sentence, because it was not heard or understood (like a reply to the question: "¿Qué dijiste?")