In my experience, business tends to be a self serving pursuit that only benefits others who already have more than they need.
You can call it rational, but lets not pretend there's any nobility in dedicating your life to the generation and maximization of private profit as an end in itself.
Education would have been a better choice in the context of this line.
I think him opting out of dementia, does not mean he didn't think life was worth living. He didn't seem depressed, just didn't want to put himself and his family through dementia.