That's what people do on the internet. They make judgements and unfair comments without having to justify their reasoning. No one who has said they think the match was fixed can point to any evidence.
Be reasonable please, what kind of proof are you waiting for? If you need a signed agreement paper to believe it, nothing to do. But for me, a little bit volleyball common sense would be enough to realize this obvious fixed match as Matthias's explained well with his arguments