@ fotoguzzi : assuming the cb by itself is ok there are only two positions : pushed in and connected or popped out and disconnected. there are no intermediate positions or possibility to disconnect electrically while physically pushed in or vice versa.
my best quess is the cb popped during first try of alt gear extension and they did not checked and tried again or truly it was popped by e.g a pilots case and they overlooked it. i doubt they forgot to look at the cb,s its one of the first things when a system in an aircraft refuses to work.
the interesting question is if they checked the cb after first try of alt gear extension or if they tried alt gear a single time and after alt gear failed just prepared for a gear up landing.
the next question is if in any case the crew can be blamed directly. does the abnormal checklist on a 767 cover the rechecking of the cb,s when alt gear fails?
when not the pilot can say- " procedures were followed, i tried alt gear, it did not work, so a gear up landing was the final result, for anything else ask the manufacturer of this aircraft and not me "