It might have something to do with attitude...
I do not want to suggest anything here but for example a lot of ex-sabena guys went on the interviews for Qatar Airways....
All the french speaking people where not accepted beceuse apparently their french accent was something almost not understandable for the Qatari pilots.
Or maybe they where not really prepared.....comming from a flag carrier does not mean thatr you do not have to study hard for your interview. The questions are rather demanding....
Or maybe there is an agreement between KLM and EK not to accept each others pilots...
Or....
Or...