Union contract. They wanted the best people, they had to lay for it.
When I applied, it was a term position, not permanent. Everyone that applied had to take an aptitude test. 90% of all applicants washed out at that point. When I tested for the permanent position that was a little better: washout rate was only 75%. But think about it. They had to test 200 people to fill 5 jobs. We were ramping up and ended up filling 300 positions. That doesn't even include the attrition rate. My first training class consisted of 10 people. Seven of us passed. Within a year, two had left. Not transfered, left. High stress. When I left after 6 years, only one other member remained.
I won't mention the other companies, but their hiring practices were warm body.