In every company there is relentless pressure to de-skill at every level so that salaries can be kept as low as possible. Those who have technical skills and legal maintenance permissions become thinly spread, supervising more and more less-skilled workers. They cannot be everywhere at once. Sooner or later someone working for them makes a major boo-boo and this a fine example.
Meanwhile the company
PR will continue to chant 'Safety is our first priority' and 'We are an industry leading centre of excellence'. It was very lucky no-one was under that 787 when it hit the ground.