I realy do not think the issue of crm is the important thing here.
Don't forget that CRM starts on the ground!
Did either pilot actually check the en-route weather or was it a case of "it looks OK outside right now, so let's go!"?
True CRM means that ANY member of the crew who has concerns, before, during or after a flight should react immediately.
A question I have on this hypothetical case is: Is this really a two crew flight or is it just coincidence that both front seats are occupied by qualified pilots and dual controls are fitted?