Well, a company like Boeing can use all the aviation safety standards and certificates and still cock up the software systems so that two passenger jets with nothing wrong with them crash killing everyone on board.
The Tacoma bridge appeared to be an engineering marvel until the wind got it to...
Didn't the ship lose contact with the sub about 90mins into their voyage but didn't report it to the coastguard for another 5 hours or so? So that can easily explain the implosion not being picked up.
Knocking sounds, something from the debris, maybe something attached by a cable or piping or...
kind of weird that resources can be chucked at 5 people in a sub, multiple aircraft, boats, drone subs etc. but a boat in the Med with 300 immigrants on board can be allowed to sink.