DB pensions really are little better than pyramid schemes and rely on the young employees funding them to pay the pensioners. When they close the onus is put upon the employer to cover every eventuality without the employee being asked to share the hardship.
It can get to the point that the employer looks at the viability of the company when they are putting a huge amount into the pension scheme, with no discernible benefit to themselves or the success of the concern. I have seen the latter and the owners run away.