Because none of it has yet been proved to be false or true. As for Amaral, he wasn't 'booted off for incompetence' as you put it, he was reassigned because he spoke to the Press and criticised the English police involvement. A Cardinal Sin for any police officer leading an investigation.
1. The Portuguese prosecutors could find no basis of criminal charges against the McCanns.
Citing the Portuguese prosecutors
ought to be all the McCanns have to do (in separate, civil, proceedings) to
prove Amaral's allegations false.
Amaral accuses the McCanns of:
Killing their daughter (not murdering her, even though the investigation Amaral, initially, headed up
did accuse the McCanns of
murder).
Amaral accuses the McCanns of profiting from a fraudulent fund.
Amaral accuses the McCanns of hiding their (dead) daughter's body and launching a fraudulent fund in their dead daughter's name.
All these things can be proven untrue.
So why did Amaral win the appeal?