How can they get so different results?
Simple. They have different sponsors.
I would completely ignore any company which gives Bitcoin a low rating. There is no ecosystem without bitcoin.
Additionally, how the hell does
IOTA gets a good grade in Weiss rating? IOTA just paid them.
IOTA is corrupted, stealing coins from users using their centralized "coordinator" which confirms transactions.
A transaction free and instant which uses a centralized validator?? No thanks, I just prefer to use Visa.
Do you think that "The China Center for Information Industry Development" is really corrupted? I don´t think so, it is a state institution, so it should have some value.
On the other hand, we do not know how these companies rate cryptocurrencies. We see only final rating and ranking, but we do not see reasons why. So until they provide facts, it doesn´t have any value.