The only explanation I have ever read, apart from the conspiracy theories that the other judges were biased, corrupt and incompetent (which clearly isn't true, because it would more likely be true the other way), was on here from
@KS55 (was it?) that it was traditional for CAS arbitrators to support the view given by the party appointing them. I am not sure if that was serious, but I was going to look through some other CAS judgments to check it out.
Don't forget though, we are dealing with people here. Nothing is guaranteed in any legal case. The club's position is clearly that they have the evidence to counter the PL's position. I think we need to respect that and trust the process.