Well there's always the key person hit by a bus scenario, that companies need to protect against.
They always want to drive down the cost of skilled labour thats just a given. This has backfired spectacularly so any times now with huge headlines thats its hardly news worthy now.
But that aside I have never found these massive documentation projects, for ISO, to be productive use of time. They are almost out of date as soon as they are written. Suggest hiring a short term contractor to do the documentation, and see what value management put on the work.
That said having a highly skilled person silo their information in themselves is not useful either. It often means that person is a roadblock for many projects as everyone has to go through them to get things done. Eventually this outweighs their usefulness.
I have kinda given up trying to explain to clueless or stubborn people how not to manage projects. I just confirm the decisions and instruction via email and don't worry about it. At some point the impact of their poor decisions dawns on them, and they start to listen.